An Investigation of Surface Water/Groundwater Relationships in a

AN INVESTIGATION OF SURFACE
WATER/GROUNDWATER
RELATIONSHIPS IN A RURAL
WATERSHED IN SOUTHERN
HONDURAS
By
Robert F. Hegemann
A REPORT
Submitted in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
GEOLOGY
MICHIGAN TECHNOLOGICAL UNIVERSITY
2011
Copyright © 2011 Robert F. Hegemann
This report titled, “An Investigation of Surface Water/Groundwater Relationships in a
Rural Watershed in Southern Honduras,” is hereby approved in partial fulfillment of the
requirements for the Degree of MASTER OF SCIENCE IN GEOLOGY.
Department of Geological and Mining Engineering and Sciences
Signatures:
Report Advisor _________________________________________
John S. Gierke, Ph.D., P.E.
Department Chair _________________________________________
Wayne D. Pennington, Ph.D.
Date _________________________________________
Table of Contents
List of Figures .................................................................................................................. v
List of Tables .................................................................................................................. vii
Acknowledgements ....................................................................................................... viii
Abstract ...........................................................................................................................ix
1
Introduction .............................................................................................................. 1
2
Background .............................................................................................................. 2
3
2.1
Location ............................................................................................................. 2
2.2
Geologic Setting ................................................................................................. 3
2.3
Motivation ........................................................................................................... 3
Methods ................................................................................................................... 5
3.1
4
Hydrologic Field Measurements ......................................................................... 6
3.1.1
Precipitation ................................................................................................. 6
3.1.2
Old Community Water Source Spring Discharge ......................................... 6
3.1.3
Caracol River Discharge .............................................................................. 8
3.2
Thornthwaite Mather Water Balance ................................................................ 10
3.3
Lineament Mapping.......................................................................................... 12
3.3.1
Field Observations ..................................................................................... 12
3.3.2
Remote Sensing Analysis .......................................................................... 13
Results ................................................................................................................... 16
4.1
Field Data Comparison .................................................................................... 16
4.2
Thornthwaite Mather Water Balance ................................................................ 19
4.3
Lineament Analysis .......................................................................................... 21
5
Conclusion ............................................................................................................. 30
6
Recommendations ................................................................................................. 31
7
References ............................................................................................................. 33
8
Appendices ............................................................................................................ 35
Appendix A : Social Context of Water Resources in El Caracol ................................. 35
Appendix B : Precipitation data for El Caracol and La Rinconada, Honduras ............ 37
Appendix C : Precipitation data for San Marcos de Colón, Honduras ........................ 38
iii
Appendix D : Water Depth Measurements ................................................................. 39
Appendix E : Timed Trials of Discharge from Hose Draining Spring .......................... 40
Appendix F : River Cross Section and Equal Area Approximations ........................... 41
Appendix G : Thornthwaite Mather Water Balance Equations ................................... 42
Appendix H : Thornthwaite Mather Water Balance Model Results............................. 44
Appendix I : Delineated Watersheds .......................................................................... 45
Appendix J : Regional Scale Lineament Interpretation .............................................. 46
Appendix K : Coincidence Raster .............................................................................. 47
iv
List of Figures
Figure 2.1 Location of study area - El Caracol, Honduras. The extent of the map is
shown in red within the inset map of Honduras. Map is based on the digital version of
the topographic map of the San Marcos de Colón quadrangle produced by the
Honduran National Geographic Institute (1989). ............................................................. 2
Figure 3.1 Location of field data acquisitions in 2010. ..................................................... 5
Figure 3.2 Rain gauges installed at El Caracol (left) and La Rinconada (right). .............. 6
Figure 3.3 V-notch weir installed at the old community water source spring in El
Caracol. ........................................................................................................................... 7
Figure 3.4 Location of weir approximation in the Caracol River with dimensions. ........... 9
Figure 3.5 Field mapped lineaments, clockwise from upper left: L1, L2, L3, L4 (as
labeled in Figure 3.1)..................................................................................................... 13
Figure 4.1 Monthly rainfall in inches for San Marcos de Colón, El Caracol, and La
Rinconada in 2010. Average monthly precipitation values for San Marcos de Colón
from 1987 to 2010 are shown in purple with bars representing the maximum and
minimum recorded values during the 37 year dataset. .................................................. 16
Figure 4.2 Comparison of rainfall and river discharge. .................................................. 17
Figure 4.3 Comparison of rainfall and spring discharge. ............................................... 18
Figure 4.4 Correlation of normalized river discharge with precipitation. ........................ 18
Figure 4.5 Correlation of normalized spring discharge with precipitation. ..................... 19
Figure 4.6 Comparison of TMWB predicted values and observed river discharge. ....... 20
Figure 4.7 Comparison of TMWB predicted values and observed spring discharge. .... 21
Figure 4.8 Lineaments interpreted from remote sensing products. ............................... 22
Figure 4.9 Comparison of regional and local lineament interpretations. ........................ 23
Figure 4.10 Rose diagrams of frequency of lineament trends (green) and trends
weighted by length (blue). ............................................................................................. 24
Figure 4.11 Comparison of field mapped features and lineament interpretations. ........ 25
Figure 4.12 Lineament interpretation from RADARSAT-1 image with several noticeable
features that correspond with lineaments interpreted from other images outlined with
dashed green boxes. ..................................................................................................... 26
Figure 4.13 Topographic relief of the El Caracol watersheds with approximate location
of the Caracol River and NW trending fracture crossing the topographic sub-watershed.
The image is displayed in the UTM zone 16N coordinate system with the northing,
easting, and elevation in meters. ................................................................................... 27
Figure 4.14 Normalized Difference Vegetation Index calculated from ASTER for the
Caracol River watershed. .............................................................................................. 28
Figure 4.15 Google Earth Imagery of the El Caracol watersheds. Image ©2011 Digital
Globe, ©2011 Google. .................................................................................................. 29
Figure 8.1 Watersheds in the area of El Caracol as delineated using ESRI ArcGIS
Desktop 9.3. The blue polygon represents the topographic watershed of the old
v
community water source spring. The red polygon denotes the sub-watershed of the
Caracol River upstream of the point where measurements were recorded. The green
polygon depicts the watershed of the Comalí River (at a point upstream of San Marcos
de Colón), of which the Caracol River is a tributary. ..................................................... 45
Figure 8.2 Coincidence raster shown along with field mapped lineaments and springs.
Watershed boundaries are included for reference. The minimum coincidence for the
raster was set at 4 according to the methodology of Bruning et al. (2011) to assure that
coincidence was not the result of a single image (ASTER and Landsat images have
three interpretations). The coincidence raster is compiled from the lineament
interpretations with a 200 m buffer (100 m each side). A buffer of 100 m and a pixel
size of 50 m were used in creating the raster to increase coincidence for the NW
trending feature in the Caracol River watershed as the feature was mapped in all
interpretations but not in an exact location. ................................................................... 47
vi
List of Tables
Table 3.1 Monthly average temperature data for San Marcos de Colón from World
Weather Online. ............................................................................................................ 12
Table 3.2 Remote Sensing Products obtained for lineament analysis. ......................... 14
Table 4.1 General trends of lineaments mapped in the field with point locations and
bearings. ....................................................................................................................... 24
vii
Acknowledgements
This report is dedicated to the residents of El Caracol who opened their homes to a
complete stranger and made me one of their own.
Thanks to Peace Corps, my fellow volunteers, and especially my supervisors Menelio
Bardales and Claudia Quintanilla for all their support during my time in Honduras and
their assistance in the various stages of research for this report.
Special thanks to Dr. John Gierke for his support in all aspects of my Peace Corps
Service and my time as a Peace Corps Master’s International student at Michigan Tech,
and to Dr. Alex Mayer and Dr. Ann Maclean for their assistance and insight as members
of my committee.
Many thanks to my fellow MTU PCMIs and grad students, including Miriam Rios
Sanchez, Carla Alonzo Contes, Briana Drake, Randall Fish, Cara Shonsey, and
Rudiger Escobar Wolf, among others, for their moral support and assistance with
unfamiliar programs and procedures.
Support for this research was provided by the NSF PIRE 0530109 grant.
viii
Abstract
Despite failed attempts at obtaining a potable water system, the village of El Caracol in
Southern Honduras remains committed to improving access to water resources. To
assist in this endeavor, an investigation of the hydrogeological characteristics of the
local watershed was conducted. Daily precipitation was recorded to examine the
relationship between precipitation and approximated river and spring discharges. A
Thornthwaite Mather Water Balance Model was used to predict monthly discharges for
comparison with observed values, and to infer the percentage of topographic
watersheds contributing to the respective discharges. As aquifer porosity in this region
is thought to be primarily secondary (i.e., fractures), field observed lineaments were
compared with those interpreted from remote sensing imagery in an attempt to
determine the usefulness of these interpretations in locating potential water sources for
a future project.
ix
1 Introduction
Unlike the neighboring countries in Central America, Honduras is not known for
earthquake and volcanic hazards. While Honduras does experience earthquakes;
hydrological hazards like drought and flooding, which often results from hurricanes, are
more significant threats (Cunningham 1984). Also of a hydrologic nature, many rural
communities in Honduras lack access to improved water sources, although the World
Health Organization (2010) states that 86% of the population of Honduras is using
improved water sources.
As a Peace Corps Volunteer assigned to the village of El Caracol, Honduras, the
author’s primary project was to work with the town council on the development of a
potable water system for the community. Due to extenuating circumstances (involving
property permissions related to the water source - Appendix A) this project was never
realized, but the author was left with a strong introduction to water resource concerns in
rural southern Honduras.
Cunningham (1984) mentions that delayed onset of the rainy season often results in
drought for southern Honduras, and Hammond (2005) adds that such periods of low
precipitation leave water sources in southern villages dry or contaminated. This
situation was experienced firsthand by the author in 2009. 2010, in contrast, was an
above average year for precipitation. Many families lost part or all of their harvest in
2009 and were forced to rely on other resources until the next harvest. While family
gardens might mitigate some of the challenges of a lost harvest, most families do not
establish garden plots because, among other reasons, gardens increase daily water
consumption, and thus the amount of work required to obtain water. Hygiene also
suffered as adequate sources for washing became harder to find.
Currently the residents of El Caracol rely on a semi-improved spring, unimproved
springs, and the Caracol River for their water needs. As the community has been
concerned with developing a potable water system for some time, the author became
interested in assisting the community with understanding and managing their water
resources. To contribute toward this goal, the author collected precipitation
measurements, spring discharge, and river discharge measurements during the rainy
season of 2010. Upon return to Michigan Technological University these data were
analyzed using a Thornthwaite Mather Water Balance Model (Dingman 2002) to gain
insight into watershed hydrology. Additionally, a lineament analysis was conducted,
building upon the work of Bruning et al. (2011), in an attempt to assist the community
with identifying springs more likely to be consistently productive due to proximity to
fractures or locating significant fractures in which a perforated well might have
increased yield.
1
2 Background
2.1 Location
El Caracol is a small village of approximately 200 inhabitants in southern Honduras near
the Nicaraguan Border. The village is part of the Aldea of San Francisco, the
Municipality of San Marcos de Colón, and the Department of Choluteca (Figure 2.1).
The community is spread along the valley of the headwaters of the Caracol River at an
elevation of roughly 1050 meters above sea level.
Figure 2.1 Location of study area - El Caracol, Honduras. The extent of the map is shown in red within
the inset map of Honduras. Map is based on the digital version of the topographic map of the San
Marcos de Colón quadrangle produced by the Honduran National Geographic Institute (1989).
Most of the population is dedicated to subsistence agriculture of corn and beans, but
families with land assets and greater access to capital maintain cattle bred for a
combination of dairy, meat, and drought resistance. Water related tasks are generally
split along gender lines with women and children fetching water for drinking, cooking,
and cleaning, while men locate water sources for livestock. Water demand in the
2
community is variable, depending on factors such as family size and proximity to water
sources (as observed by the author), even though the majority of residents rely on a
single semi-improved spring for drinking water. The burden of meeting household water
needs increases in the dry season as local sources dry up, forcing households to travel
further in search of water.
2.2 Geologic Setting
Little is known about the geology of the region of San Marcos de Colón. A geologic
quadrangle map (1:50,000 scale) has yet to be produced for the region and the national
level geologic map of Honduras (1:1,000,000 scale) does not provide much information.
The region is underlain by the Padre Miguel Formation consisting mostly of ignimbrites
(Williams and McBirney 1969; Rogers 2003). The Hydrogeological Map of the Southern
Zone of Honduras (1993) classifies aquifers within the region of San Marcos de Colón in
the Padre Miguel Formation as “extensive, moderately productive, fissure flow” aquifers,
interpreted to indicate that porosity is mostly secondary. Regional fracturing in
Honduras trends NE and NW, including some N/S features, and the fracturing controls
topography and drainages, as well as volcanism during the Quaternary Period (Williams
and McBirney 1969; Manton 1987). The Department of Choluteca, which includes the
town of San Marcos de Colón, displays one regional feature known as the Choluteca
Lineament. The Choluteca Lineament is thought to influence the course of the
Choluteca River in this zone and is potentially linked to the Guayape Fault System; a
major NE trending feature in Honduras (Manton 1987; Cáceres and Kulhánek 2000;
Nelson et al. 2002).
2.3 Motivation
Drilled wells are not common in the region surrounding El Caracol as surface water is
often accessible. However, surface water is likely contaminated by cattle, pesticide
runoff from agricultural fields, and washing/bathing (personal observation). Additionally,
the dry season from November to April is quite pronounced (reference Figure 4.1 for
rainfall distribution), making access to a reliable water source a concern. Families in El
Caracol have adapted to the disparity between the wet and dry seasons in a variety of
ways.
Examples of adaptation include setting up rain barrels in the rainy season to capture
roof runoff for washing to avoid the risk of flash flooding while washing in the river, and
the use of rolls of electrical conduit to siphon water from distant sources to a personal
storage tank. Nevertheless, families distant from the community center often do not
have access to the capital required to invest in such strategies, and are forced to travel
farther and farther to meet their water needs as the dry season progresses, especially
to obtain drinking water as smaller springs dry up. As a result, the El Caracol town
3
council has established the construction of a public water distribution system as a
priority.
With the possibility of electricity arriving to El Caracol in the near future, the community
is considering the prospect of drilling a well, in light of two failed attempts to secure a
privately owned source for a potable water system. Therefore the motivation behind
this study was to provide hydrogeological information to community members that might
assist in decisions about future potable water source prospects. With this in mind,
hydrologic data were collected, in a manner that could be replicated by the community
members, to assess watershed characteristics for use in conjunction with a map of
geologic lineaments to highlight potential locations of suitable water sources.
4
3 Methods
In the area surrounding El Caracol, during the rainy season of 2010, hydrologic data
including precipitation, spring discharge, and river discharge measurements were
collected in the field. Additionally five springs and 17 lineaments were mapped in the
field with four lineaments traced and 13 recorded as points with bearings. The
respective locations of field observations are shown in Figure 3.1.
Figure 3.1 Location of field data acquisitions in 2010.
Hydrologic data were then compiled for further analysis, incorporating the use of a
Thornthwaite Mather Water Balance Model. Field mapped lineaments were
subsequently compared with lineaments interpreted from remote sensing products
based on the methodology proposed by Bruning et al. (2011). The methods used in this
investigation are further described in the following sections.
5
3.1 Hydrologic Field Measurements
3.1.1 Precipitation
Daily Precipitation measurements were collected using Accurite rain gauges with
demarcations in inches (Figure 3.2). Rainfall was measured from 1 April 2010 to 19
September 2010 at the primary gauge installed near the old community water source
spring in El Caracol. A secondary rain gauge was installed downstream at La
Rinconada to provide measurements for comparison from 22 May 2010 to 19
September 2010 (Appendix B). The author considered locating a rain gauge in the
mountainous headwaters of the Caracol River to assess precipitation variability, but
residents insisted that the remote location would lend to theft of and/or tampering with
the gauge. Observations were made daily with the assistance of volunteers. Every
morning the gauge was emptied with the precipitation total recorded in a field notebook.
Figure 3.2 Rain gauges installed at El Caracol (left) and La Rinconada (right).
3.1.2 Old Community Water Source Spring Discharge
The distance from the water surface to a reference point was recorded for the old
community water source spring. Once the water level rose to the point that the spring
began to flow over the low end, a 90° V-notch weir was installed for measuring
discharge on 16 June 2010 (Figure 3.3). The height above the notch was recorded in a
6
field notebook (Appendix D) and entered in the 90° V-notch weir equation from
Appendix 6.C of Groundwater and Wells (Sterrett 2007):
5
𝑄 = 2.49𝐻 2
(1)
where Q is discharge (ft3/s) and H is height above the notch (ft).
Figure 3.3 V-notch weir installed at the old community water source spring in El Caracol.
The consistency of discharge measurements was less than ideal because the weir was
removed by vandals several times and had to be located and reinstalled. Additionally,
on 9 July 2010 a hose was placed in the spring to siphon water to a personal storage
tank, and it was not until 29 July 2010 that permission was obtained to measure
discharge at the hose output to account for total discharge. The hose discharge was
recorded as an average of 3 trials of time required to fill three liters (Appendix E). The
discharge at the hose output was then added to the discharge measured at the weir
immediately afterward, assuming equilibrium state was attained at the time of
measurement.
7
It should be noted that discharge values obtained by these methods are
approximations, particularly as the ideal conditions for weir use and measurement
(Dodge 2001; Sterrett 2007) are not met. Typically, 90° v-notch weirs are suitable for
small discharges less than 5 ft3/s. Ideally, 90° v-notch weirs should be between 0.03
and 0.08 inches thick and installed level and perpendicular to flow in a straight section
of the channel. Measurements of H greater than 0.2 feet, with downstream water
surface at least 0.2 feet below the weir notch, are recommended to prevent submersion
of the weir and inhibit flowing water from clinging to the weir on the downstream side;
both of which impact accuracy. H should be measured upstream of the weir at a
distance at least 4 times greater than the maximum H to avoid irregularities as the water
approaches the weir. The weir opening should be a distance of at least 2 times H from
the sides of the channel, and the height of the weir notch above the lowest point in the
channel should be at least two times H. Maintenance is required to ensure that the weir
is not undermined and sediment does not build up on the upstream side of the weir.
While many of these conditions for 90° v-notch weirs were not met, these were the best
methods available to assess the spring discharge under the circumstances. Because of
the very low flows observed for this spring, satisfying the ideal conditions for a weir were
probably not critical since there were no apparent flow disruptions upstream of the weir.
3.1.3 Caracol River Discharge
Starting 13 July 2010 depth of water was measured using a marked pole at a point in
the Caracol River where flow is narrowed just before a waterfall, approximating a
rectangular/trapezoidal weir. The profile is composed of 2 separate trapezoids (Figure
3.4) for which the equivalent rectangular area was calculated.
The depth of water was recorded in a field notebook (Appendix D) and entered in
rectangular weir equation from Appendix 6.C of Groundwater and Wells (Sterrett 2007):
𝑄 = 3.33(𝐿 − 0.2𝐻)𝐻1.5
(2)
where Q is discharge (ft3/s), L is the length of the weir opening (ft), and H is depth of
flow (ft). For water depths of 9 inches or less, a weir length of 26 inches was used to
approximate the area of the smaller trapezoid with a 9-inch by 26-inch rectangle. When
water depths exceeded 9 inches, the smaller rectangular approximation was assumed
to be full and the resultant discharge was added to a second calculation using water
depth subtracted by 9 inches, and a weir length of 89 inches to approximate the area of
the larger trapezoid with a 52-inch by 89-inch rectangle. It is important to note that
depth measurements were recorded in the early morning to avoid peak flood discharges
from afternoon rains.
8
Figure 3.4 Location of weir approximation in the Caracol River with dimensions.
Discharge values were compared with the resulting discharges from the trapezoidal
(Cipoletti) weir equation from Chapter 7 of the Water Measurement Manual (Dodge
2001):
3
𝑄 = 3.367𝐿𝐻 2
(3)
For water depths of 9 inches or less, a weir length of 20 inches was used to represent
the smaller trapezoid. When water depths exceeded 9 inches, the smaller trapezoid
was assumed to be full and the resultant discharge was added to a second calculation
using water depth subtracted by 9 inches, and a weir length of 68 inches to represent
the larger trapezoid. These values were on average 20% less than those calculated
with the rectangular weir equation. Additionally, equal area trapezoids were calculated
to establish the 1:4 horizontal to vertical side slope requirements of the equation. In this
scenario, a weir length of 23.75 inches was used for water depths of 9 inches or less to
approximate the area of the smaller trapezoid. As previously mentioned, when water
9
depths exceeded 9 inches, the smaller trapezoid approximation was assumed to be full
and the resultant discharge was added to a second calculation using water depth
subtracted by 9 inches, and a weir length of 76 inches to approximate the area of the
larger trapezoid. The values resulting from the trapezoidal weir equation using this
method were on average 10% less than those calculated by the rectangular weir
equation. Reference Appendix F for river cross section dimensions and equal area
approximations used in the weir equations.
It should be noted that discharge values obtained by these methods are approximations
as the river cross section is neither a rectangle nor a trapezoid with 1:4 side slopes, and
the ideal conditions for weir use and measurement (Dodge 2001; Sterrett 2007) are not
met. Ideally, rectangular and trapezoidal weirs, like v-notch weirs, should be between
0.03 and 0.08 inches thick and installed level and perpendicular to flow in a straight
section of the channel. Measurements of H greater than 0.2 feet, with downstream
water surface at least 0.2 feet below the weir notch, are recommended to prevent
submersion of the weir and inhibit flowing water from clinging to the weir on the
downstream side; both of which impact accuracy. H should be measured upstream of
the weir at a distance at least 4 times greater than the maximum H to avoid irregularities
as the water approaches the weir. The weir opening should be a distance of at least 2
times H from the sides of the channel, the height of the weir opening above the lowest
point in the channel should be at least two times H, and H should not be greater than
one third of the length of the weir opening. Maintenance is required to ensure that the
weir is not undermined and sediment does not build up on the upstream side of the
weir. Many of these conditions were not met as no actual weir was installed, however,
these were the best available methods to assess the river discharge under the
circumstances. Unlike the flow conditions for the spring, the river flows were obviously
turbulent most of the time, so the approximations used to translate depth of flow to
discharge is less reliable for the river flow. Nevertheless, the difference in the estimated
flows for the rectangular and trapezoidal weir approximations is only about 20% for the
conditions of this river section. It is likely that the other ideal conditions cause similar or
less deviations.
3.2 Hydrologic Data Analysis
3.2.1 Precipitation/Discharge Comparison
Precipitation data were plotted alongside discharge approximations from the Caracol
River and old community water source spring to evaluate in trends in the daily values.
Additionally, discharge values were normalized by watershed area and plotted against
precipitation values to assess correlation. Watershed areas used in the normalization
were calculated from polygons created using a combination of the hydrology tools within
10
ESRI ArcGIS Desktop 9.3 and topographic boundaries delineated from contours
generated from a digital elevation model (DEM).
Cross-correlation analysis (Lee and Lee 2000) was conducted by shifting the
precipitation input chronologically in an attempt to infer groundwater residence time.
Precipitation was plotted against discharge values recorded days, weeks, and up to a
month later to assess correlation based on changes in R2 values. However, the dataset
is not of a sufficient duration to analyze cross-correlations for lag times on the order of
months, such as those found in the study by Kucharski (2010).
3.2.2 Thornthwaite Mather Water Balance
Precipitation data from El Caracol were entered in a Thornthwaite Mather Water
Balance (TMWB) model adapted from Dingman (2002) using the Hamon method
(Appendix G) to assess the hydrogeological characteristics of the area. The TMWB
model was selected considering that the model input requirements (monthly
precipitation, average monthly temperature, latitude of the site location, root zone
thickness, and soil field capacity) are site specific and compatible with available data.
The Hamon method calculates potential evapotranspiration based on the
thermodynamic relationship between temperature and relative humidity and is reported
to provide acceptable values for potential evapotranspiration in forested catchments in
the Eastern United States with a calibration coefficient varying from 1 to 1.2, north to
south (Pyzoha et al. 2008; citations within).
In the TMWB model, water enters into storage as soil moisture when precipitation
exceeds potential evapotranspiration as calculated by the Hamon method. Likewise,
when the field capacity of the soil is exceeded, the excess water results in
runoff/recharge values which can be compared with observed discharges. Calvo (1986)
states that the TMWB model, though developed from North American conditions, is
applicable to predicting monthly stream flows in neighboring Costa Rica, and Xu and
Singh (1998) state that more complex models involving additional parameters do not
necessarily yield more reliable results.
Monthly average temperature values (Table 3.1) were obtained from World Weather
Online (2011) for San Marcos de Colón and entered into the TMWB model along with
the El Caracol precipitation data. San Marcos de Colón, at a distance of approximately
15 km from El Caracol, is the nearest location for which monthly average temperature
data were available, although the actual location where temperature measurements
were collected could not be confirmed.
11
Table 3.1 Monthly average temperature data for San Marcos de Colón from World Weather Online.
Month
High
Low
Average
Jan
31°c
22°c
Feb
33°c
23°c
Mar
33°c
23°c
Apr
32°c
23°c
May
31°c
23°c
Jun
30°c
23°c
Jul
31°c
24°c
Aug
32°c
24°c
Sep
29°c
22°c
Oct
28°c
22°c
Nov
30°c
22°c
Dec
30°c
22°c
26.5
28
28
27.5
27
26.5
27.5
28
25.5
25
26
26
A root zone depth of 0.5 meters and a soil field capacity of 0.2 were selected as
reasonable median values based on a similar studies by Shonsey (2009) and Kucharski
(2010). The El Caracol TMWB model was insensitive to changes in root zone depth
and soil field capacity values and therefore these values were assumed to be
reasonable for the scope of this study.
Monthly precipitation data were acquired from the Honduran Secretary of Natural
Resources (SERNA) from 1973 to 2010 for the San Marcos de Colón watershed
(Appendix C). These data were entered into a separate TMWB model for San Marcos
de Colón using the same root zone depth and soil field capacity values to provide a
comparison for the El Caracol model with a more robust dataset.
Additionally, the areas of the Caracol River sub-watershed and the watershed of the old
community water source spring were calculated to convert the runoff/recharge values
generated by the TMWB model into monthly average discharges for comparison with
observed discharges. The areas were calculated from watershed polygons created
using a combination of the hydrology tools within ESRI ArcGIS Desktop 9.3 and
topographic boundaries delineated from contours generated from a digital elevation
model (DEM).
The TMWB model is limited in this application as the model does not distinguish
between runoff and recharge. It is reasonable to assume that recharge enters the
Caracol River at some point after a precipitation event to contribute to discharges
alongside runoff. However, it is not probable that runoff enters the spring system. As
the TMWB model does not separate runoff, the resulting runoff/recharge values likely
overestimate spring discharge. In addition, the model does not incorporate a
groundwater storage component and cannot generate runoff/recharge during periods of
no precipitation. Therefore, when analyzing dry season discharges it is necessary to
integrate aquifer storage similar to the study by Fish (2011).
3.3 Lineament Mapping
3.3.1 Field Observations
Four lineaments were mapped in the field with a Garmin GPSmap 60CSx unit using the
tracks function, and points and bearings were recorded for 13 lineaments in the
12
immediate El Caracol area for comparison with lineaments mapped with remote sensing
products (Figure 3.5, Figure 3.1). Lineaments were identified as linear features
crossing local topography with cliffs and/or rock outcrop traces present along the length
of the feature. Water was usually present along these features; however water might be
absent in the dry season. The possibility exists that some drainages were mistakenly
identified as lineaments as physical evidence of faulting/fracturing in outcrops was not
observed due to weathering and vegetation.
Figure 3.5 Field mapped lineaments, clockwise from upper left: L1, L2, L3, L4 (as labeled in Figure 3.1).
3.3.2 Remote Sensing Analysis
To analyze lineaments in the area, the methodology proposed by Bruning et al. (2011)
was followed. In this methodology, different types of imagery, and digital products
derived from them, are used to map lineaments taking advantage of the different
spectral and spatial resolutions. In using several images/products, a more accurate map
of lineaments likely to be of geological origin can be produced. These lineament
interpretations are combined into a single lineament map by doing a coincidence
analysis. The steps for the coincidence analysis are described in Bruning et al. (2011)
13
Three satellite images (Landsat 7 ETM+, ASTER, and RADARSAT-1) and a digital
elevation model (DEM) were obtained to conduct a lineament analysis. All images have
acquisition dates falling within the dry season, which occurs on average from November
to April. Information on image/product acquisition dates and sources is listed in Table
3.2.
Table 3.2 Remote Sensing Products obtained for lineament analysis.
Product
Landsat 7
ETM+
ASTER
Acquisition
Date
11/15/1999
1/29/2004
ASTER DEM
(30 m)
RADARSAT-1
4/17/2008
Source
Glovis USGS
http://glovis.usgs.gov/
WIST NASA
https://wist.echo.nasa.gov/~wist/api/imswelcome/
WIST NASA
https://wist.echo.nasa.gov/~wist/api/imswelcome/
URSA ASF
https://ursa.asfdaac.alaska.edu/cgi-bin/login/guest/
Prior to analysis, the RADARSAT-1 image was orthorectified and georeferenced using
ASF MapReady 2.3, making use of the Aster 30 m DEM resampled to 7 m to
accommodate the spatial resolution of the RADARSAT-1 image. Pre-processing,
including atmospheric correction of bands 1, 2, and 3 by histogram subtraction and
stacking of image layers, was performed on ASTER and Landsat ETM+ images in
ERDAS IMAGINE 9.3. All images were projected to the World Geodetic System 1984
(WGS 84), Universal Transverse Mercator zone 16 North (UTM Zone 16N), coordinate
system. Digital image processing, including Principal Component Analysis (PCA)
performed in ERDAS IMAGINE 9.3 and band combination and stretching carried out
using ESRI ArcGIS Desktop 9.3, was conducted on the ASTER and Landsat ETM+
images. Hillshades with illumination angles of 235° and 315°, selected to highlight
linear features of different orientations, were derived from the DEM using ESRI ArcGIS
Desktop 9.3. The hillshades were then used in combination with the DEM for
interpretations.
For each digital image/product, lineaments were visually interpreted in the study area
and digitized in ESRI ArcGIS Desktop 9.3. A separate file was created for each product
and image band combination to maintain separate interpretations. These lineaments
were compared with a composite map of regional lineaments interpreted from Landsat 7
ETM+, ASTER, RADARSAT-1, and DEM derived products. The trends of the regional
lineaments were then plotted in rose diagrams for comparison with the regional fault
trends to assist in the evaluation of the lineament interpretations against the field
14
mapped lineaments. Additionally, the Normalized Difference Vegetation Index (NDVI)
(Meijerink et al. 2007) was calculated for the ASTER image using ESRI ArcGIS Desktop
9.3. The NDVI was used to compare the dry season vegetation patterns, which indicate
the possible presence of groundwater, with fractures in the Caracol River subwatershed, upstream of the point where discharge measurements were recorded.
15
4 Results
4.1 Field Data Comparison
The San Marcos de Colón regional monthly rain distribution is bimodal as shown in
Figure 4.1. During the rainy season (roughly May to October) there is an approximately
one-month period around June/July where there is a significant drop in the amount of
precipitation, a time which locals refer to as the “canicula”. Annual precipitation is
known to vary with El Niño/La Niña cycles and hurricane events; however annual
variation was not investigated in this study. Nevertheless, with 99.26 inches of recorded
precipitation, rainfall in 2010 was substantially above the 45.63 inch average for the
1973 -2010 dataset, and should not be assumed to represent an average year.
Observed precipitation values at La Rinconada and El Caracol in 2010 also follow this
trend, despite an elevation difference of approximately 100 meters and lateral
separation of approximately 15 kilometers. Additionally, there is anecdotal evidence
that 2010 was a wetter than average year for El Caracol.
Figure 4.1 Monthly rainfall in inches for San Marcos de Colón, El Caracol, and La Rinconada in 2010.
Average monthly precipitation values for San Marcos de Colón from 1987 to 2010 are shown in purple
with bars representing the maximum and minimum recorded values during the 37 year dataset.
Precipitation in El Caracol and La Rinconada in September is likely under-represented
because observations ceased on 19 September 2010. The average daily precipitation
was calculated from the recorded values in September and entered as an
approximation for the missing dates to account for the lack of recorded measurements.
Similarly, the value for La Rinconada in May is artificially low because the gauge was
not installed until 21 May 2010.
16
Comparable to the observed rainfall, the average monthly river and spring discharges
are also bimodal and, when analyzed on a daily level, the timing of observed variations
in discharge appears to correlate well with rainfall events (Figure 4.2, Figure 4.3).
River Discharge
El Caracol Rain Gauge
0
75
5
50
25
0
5/1/2010
6/1/2010
7/1/2010
8/1/2010
9/1/2010
Precipitation (inches)
Discharge (cubic feet per second)
100
10
Figure 4.2 Comparison of rainfall and river discharge.
It should be noted that gaps in discharge data do not indicate periods of no flow but
rather dates for which observations were not collected. Furthermore, the gap in river
discharge on July 21, 2010 in Figure 4.2 is the result of the river stage height being too
high to measure due to precipitation from Tropical Storm Agatha. Precipitation,
however, was measured daily as volunteers recorded daily precipitation totals when the
author was not present.
17
Spring Discharge
El Caracol Rain Gauge
0
0.04
0.03
5
0.02
Precipitation (inches)
Discharge (cubic feet per second)
0.05
0.01
0
5/1/2010
6/1/2010
7/1/2010
8/1/2010
9/1/2010
10
Figure 4.3 Comparison of rainfall and spring discharge.
Normalized River Discharge (inches)
Spring discharge has a higher correlation with precipitation as measured at the El
Caracol Rain Gauge than the river discharge (Figure 4.4, Figure 4.5). This is likely due
to the location of the river headwaters at higher elevations in more mountainous terrain
that may influence local precipitation.
1.5
R² = 0.48
1
0.5
0
0
1
2
Precipitation (inches)
Figure 4.4 Correlation of normalized river discharge with precipitation.
18
3
Normalized Spring Discharge (inches)
0.03
R² = 0.59
0.02
0.01
0
0
1
2
Precipiation (inches)
3
Figure 4.5 Correlation of normalized spring discharge with precipitation.
Cross-correlation analysis for the spring, conducted by shifting the precipitation input
chronologically (Lee and Lee 2000), indicates that the strongest correlation between
precipitation and discharge occurs within the day of the of the recorded observations.
This result suggests that the groundwater system is heavily influenced by surface water
infiltration with little delay between rain events and peak flows. However, the dataset is
not of a sufficient duration to analyze cross-correlations for lag times on the order of
months, such as those found in the study by Kucharski (2010). Therefore, the
possibility of a long residence time for groundwater cannot be discounted, especially as
correlations between precipitation and discharge for both the spring and river indicate a
base flow component to the discharges.
4.2 Thornthwaite Mather Water Balance
The normalized discharge approximations cannot be compared directly to TMWB
predicted monthly recharge/runoff values (Appendix H) because sufficient daily values
were not recorded to accurately represent a complete monthly total of normalized
discharges for some months. Therefore the TWWB predictions were converted to
monthly average discharges incorporating the watershed areas of the Caracol River and
the old community water source spring. The area of the watersheds (Appendix I) was
calculated polygons created using a combination of the hydrology tools within ESRI
ArcGIS Desktop 9.3 and topographic boundaries delineated from contours generated
from the digital elevation model (DEM).
19
When compared with observed discharge approximations, the converted TMWB
predictions yield higher than expected monthly average discharges (Figure 4.6, Figure
4.7). In the case of the Caracol River, the predicted values fall within the range of
observed discharges (note that observed discharges are 10-20% lower when calculated
with the trapezoidal weir equation compared to the rectangular weir equation).
However, the monthly average is lower than the monthly average predicted by the
TMWB calculations. The TMWB calculations for the month of September are biased as
a result of the incomplete rainfall record for this month (observations ceased on 19
September 2010). To compensate for the lack of recorded precipitation, the average
daily average precipitation was calculated from the recorded values in September and
entered as an approximation of the missing dates.
TMWB River predicted monthly average
River
River monthly average
100
CFS
75
50
25
0
5/1/2010
6/1/2010
7/1/2010
8/1/2010
9/1/2010
Figure 4.6 Comparison of TMWB predicted values and observed river discharge.
The discrepancy is even larger between the TMWB predicted values and observed
values for the spring, where observed discharges are orders of magnitude below
predicted values. While this may partially result from the inability of the TMWB model to
separate runoff from the spring discharge predictions, it is the opinion of the author that
runoff along cannot account for a difference of this magnitude. There are no large
impervious surfaces in the area of El Caracol so it is unlikely that the runoff component
is more significant than recharge. However, recharge is not negligible, especially during
high volume - short duration precipitation events.
One would expect that with shallow groundwater flow and low residence time that
discharges would be highly dependent on topography. However, the higher
Thornthwaite Mather Water Balance values may result from the possibility that the
watersheds, delineated solely on the basis of topography without taking into account
20
fractures, overestimate the effective area for which runoff/recharge from precipitation
contributes to the Caracol River and spring discharges.
TMWB Spring predicted monthly average
Spring
Spring monthly average
CFS (log scale)
1
0.1
0.01
0.001
0.0001
5/1/2010
6/1/2010
7/1/2010
8/1/2010
9/1/2010
Figure 4.7 Comparison of TMWB predicted values and observed spring discharge.
4.3 Lineament Analysis
As TMWB predicted discharges did not match observed discharges, and field
observations noted that many springs appeared to have geologic controls, a lineament
analysis was conducted to assess faulting/fracturing in the area surrounding the village
of El Caracol. The area is likely to be substantially fractured based on the quantity of
interpreted lineaments (Figure 4.8). The repetitive nature of the interpreted lineaments
in Figure 4.8 suggests that author’s memory influenced the mapping of the lineaments;
i.e. that features seen in one interpretation were remembered in subsequent
interpretations. However, it should be noted that the interpretations of different products
and image band combinations were produced on different days, and the author was
careful to not compare one interpretation with another until the entire analysis was
complete.
21
Figure 4.8 Lineaments interpreted from remote sensing products.
Lineaments mapped on the regional scale (Appendix J) overlap well with lineaments
mapped in the general El Caracol area, and the two major NW trending lineaments
seen in the El Caracol watershed are clearly delineated in the regional lineament
interpretations (Figure 4.9).
22
Figure 4.9 Comparison of regional and local lineament interpretations.
The trends of the regional lineaments (Figure 4.10) correspond reasonably well with the
NE, NW, and N/S fracture trends mentioned in literature (Williams and McBirney 1969;
Manton 1987) when plotted on a rose diagram by frequency of occurrence. When the
analysis is weighted by length, assuming longer features are more prominent and thus
more important tectonically, the resulting principal direction is NE which is consistent
with the directional trend of the major regional feature, Choluteca Lineament (Cáceres
and Kulhánek 2000).
23
Figure 4.10 Rose diagrams of frequency of lineament trends (green) and trends weighted by length
(blue).
Additionally, these trends coincide with the trends of lineaments mapped in the field
(Table 4.1). These correlations lend confidence to the lineaments interpreted from the
remote sensing products.
Table 4.1 General trends of lineaments mapped in the field with point locations and bearings.
Lineament
L5
L6
L7
L8
L9
L10
L11
L12
L13
L14
L15
L16
L17
Trend
290°
290°
270°
290°
310°
200°
190°
260°
240°
240°
180°
180°
180°
In general, lineaments mapped in the field were of a small scale such that they were not
directly delineated among the lineaments interpreted from the remotely sensed imagery
(Figure 4.11). However, when taking into account GPS measurement error and bias in
the interpretation of lineaments, proximity allows visual extrapolation between some
mapped features and interpretations.
24
Figure 4.11 Comparison of field mapped features and lineament interpretations.
The ASTER image appears to yield the best interpretations in the immediate area of El
Caracol, when compared with field mapped features. However, the RADARSAT-1
image was the only image from which the field mapped lineament L2 was interpreted.
Several noticeable features within the Caracol River sub-watershed were missed in the
original analysis of the RADARSAT-1 image (dashed green boxes in Figure 4.12). They
were not included in the lineament interpretations from the RADARSAT-1 image as they
only were apparent to the author after the interpretations from the other images and
products were analyzed. While the absence of the features in the original analysis is
likely due to the inexperience of the author, these features highlight the subjective
nature of the analysis in that they were only subsequently recognizable when compared
with other image interpretations. In line with the findings of Bruning et al. (2011), it is
possible that the RADARSAT-1 image would yield improved interpretations for a more
experienced analyzer.
25
Figure 4.12 Lineament interpretation from RADARSAT-1 image with several noticeable features that
correspond with lineaments interpreted from other images outlined with dashed green boxes.
The quality of the ASTER and RADARSAT-1 image interpretations may be due in part
to the greater spatial resolution (15 m and 6.25 m, respectively) compared to the
Landsat 7 ETM+ imagery and the DEM and hillshade products (28.5 m and 30.45 m,
respectively), as the El Caracol field area is substantially less than five square
kilometers. As a result of this small scale and inconsistencies in interpreting features
across images, the coincidence raster (Appendix K), generated by similar methods to
those used in Bruning et al. (2011), was too generalized for analysis and was not used
in this study.
Despite the difficulties arising from the small scale, the lineament analysis suggests that
watershed hydrology is likely affected by fractures. As previously mentioned, two major
NW trending features were observed in the Caracol River sub-watershed within the
majority of interpretations, including the regional scale. One fork of the Caracol River
headwaters follows the more northern lineament, while the more southern lineament
26
bypasses the main river channel upstream of the point where discharge measurements
were taken and extends to a point further downstream (Figure 4.13).
N
Figure 4.13 Topographic relief of the El Caracol watersheds with approximate location of the Caracol
River and NW trending fracture crossing the topographic sub-watershed. The image is displayed in the
UTM zone 16N coordinate system with the northing, easting, and elevation in meters.
As a fracture, this interpreted lineament may direct some recharging groundwater that
would otherwise enter the Caracol River headwaters to a point further downstream.
This would tend to reduce discharge values upstream of the lineament, and could be
confirmed by measuring discharge further downstream where the groundwater captured
by the lineament would enter the river channel. The NDVI derived from the 2004 image
also displays this feature (Figure 4.14).
27
Figure 4.14 Normalized Difference Vegetation Index calculated from ASTER for the Caracol River
watershed.
Higher NDVI values (lighter in this image) indicate healthy vegetation and, by proxy, the
presence of groundwater in the dry season (Meijerink et al. 2007). The possibility of this
interpreted fracture affecting watershed hydrogeology is also supported by the field
observation of many springs and seeps near the village of Sabana Larga (Figure 4.11),
which falls along this lineament. Vegetation in the El Caracol area, as seen in an image
from Google Earth (Figure 4.15), is controlled by linear features that correspond well
with interpreted lineaments. The pattern of corroborates the NDVI values derived from
the ASTER image, and as the image is from the end of the dry season (acquisition date
of 4/6/2005), it is likely that groundwater is present along the fracture traces.
28
Figure 4.15 Google Earth Imagery of the El Caracol watersheds. Image ©2011 Digital Globe, ©2011
Google.
The topographic watershed of old community water source spring is also affected by a
lineament observed in several remote sensing products (Figure 4.11). The interpreted
lineament bisects the watershed and may potentially drain water outside of the
watershed to the NW. Additionally, a smaller scale lineament observed in the field (L1),
that appears to correspond with this interpreted lineament, bypasses the spring to
connect with the river channel (Figure 3.1). This feature may convey away recharging
groundwater that might otherwise contribute to the spring discharge.
When the watershed area used to convert Thornthwaite Mather Water Balance Model
runoff recharge values into monthly average discharges is varied, the resulting
discharge predictions indicate that an area on the order of 1% of the topographic
watershed contributes to the old community water source spring discharges. Therefore
it is probable that other springs and/or streams fall within the spring’s topographic
watershed and need to be included within the water balance analysis. Furthermore, the
aforementioned field-mapped lineament (L1 in Figure 3.1) crossing the spring
watershed was observed to carry running water in the wet season and thus likely
contributes to the reduction of the effective area of the spring watershed.
29
5 Conclusions
Based on the results of this study, it is advisable to conduct an assessment of
lineaments when investigating the hydrogeology of watersheds in areas where bedrock
is shallow and where subterranean flows are potentially controlled by fractures, such as
the volcanic terrain surrounding the village of El Caracol. Watershed boundaries can
then be evaluated on the basis of whether fractures crossing topographic boundaries
may contribute to, or withdraw from, the watershed to determine an effective area for
use in water balance calculations. In the case of the old community water source spring
watershed, it is likely that the field-mapped lineament (L1) reduces the effective area of
the watershed contributing to the spring as TMWB values indicate that around 1% of the
topographic watershed is contributing to spring discharges.
Lineaments mapped in the area of El Caracol appear to be affecting local hydrogeology
and may account for some of the discrepancy between the discharges predicted by
Thornthwaite Mather Water Balance Model and the observed discharges. From these
observations, it is likely that watersheds in the region are dependent on more than basic
topographic boundaries. Used together, lineament analyses and water balance models
can be beneficial in helping communities in developing countries to assess the geologic
factors influencing their water resources. For example, advocating protection and
reforestation of a topographic watershed may not be sufficient to improve water quality
and promote groundwater recharge if a fracture transects the watershed. Such a
fracture might introduce contaminants from outside the topographic boundary, or
transport groundwater to another watershed, impacting local water resources.
Springs are important local water resources that are often overlooked in designs for
community water systems. In the case of El Caracol, a single semi-improved spring
currently supplies over half of the community with drinking water. In similar situations
with dispersed populations and a lack of infrastructure, it may be appropriate to
investigate improving spring sources before considering a centralized, large scale
potable water distribution system. It is important to investigate the local hydrogeology
when devising solutions to community water supply needs to ensure future
sustainability.
30
6 Recommendations
In further studies of this nature it is imperative to assure community involvement from an
early stage in the project. In this study community members were drawn to the idea of
measuring precipitation, likely for the indirect relation to agricultural production, but were
rather uninterested in, and even distrustful of, discharge measurements. While it was
not challenging to convince community members to record precipitation measurements
when the author was not present, few supported efforts to measure discharge, and
there was strong disinterest in assisting the author with attempts to measure discharge
of the current community water source. With earlier concentrated efforts to promote
community involvement, it is likely the author would not have experienced setbacks
such as the weir removal and obtaining permission to measure discharge at the location
of the hose filling the personal tank. Community cooperation is essential to establish
baseline datasets of discharge and precipitation. A substantial baseline dataset,
encompassing several wet season/dry season cycles, is necessary to evaluate
groundwater storage and availability in El Caracol, and predict flow duration in drought
periods.
It is also critical to incorporate local knowledge. Community members are
knowledgeable on the locations of springs and intermittent streams that could be useful
to map and/or measure. Local knowledge is likely to assist in compiling a more
complete and robust dataset. In this study the author focused on local springs with
potential for discharge measurement. However, a GPS database of known springs in
the area would have contributed to the evaluation of the lineament analysis in the area
surrounding El Caracol.
Scale must be taken into account in future studies. In this study, bias was introduced
into field based measurements due to the location of the author as a Peace Corps
Volunteer within a specific community. As a result, the field mapping of lineaments
centered around this community and the located lineaments were of a small scale not
readily delineated from the remotely sensed imagery. Care should be taken to
incorporate a broad scale so as not to miss pertinent observations. Likewise, it is
desirable to measure precipitation and discharge at several locations, both in the
headwaters and downstream, and even outside of the immediate sub-watershed, to
properly investigate the hydrogeological impact of lineaments that transect watersheds.
Future work in El Caracol regarding water resource assessments would benefit from the
establishment of a baseline dataset of precipitation and discharges during multiple dry
and wet seasons. This baseline dataset should incorporate a catalog of springs
characterized by seasonal variability, proximity to established households, and potential
yield to assist the community with making decisions concerning access to water
resources. Additionally, if the community were to decide that drilling a well for a
31
communal water source is viable, further investigation of the lineament transecting the
watershed of the old community water source spring (L1) is warranted. This fracture
appears to be a suitable location for a well based on proximity to the center of highest
population density, and the perceived influence on the watershed, and geophysical
analysis for the presence of water along the fracture would aid in the determination of a
location for well emplacement.
32
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34
8 Appendices
Appendix A: Social Context of Water Resources in El Caracol
The residents of El Caracol are essentially members of one large extended family;
however, many divisions exist on the basis of income, religion, and other factors that
contribute to status within the community. These factors inhibit the community from
acting in a cohesive manner in matters of community improvement. Additionally,
conditions of life being what they are, the residents are natural skeptics and few
community members are willing to contribute resources, which they might need for a
rainy day, to a cause they have little faith in and see to be relatively out of their hands.
Therefore, it takes a strong community leader to garner sufficient community support to
carry out a project, but he or she undoubtedly steps on toes in the process.
This is what happened to the current president of the El Caracol town council in the first
attempt to establish a community-wide potable water project. A suitable spring source
was decided upon, a reasonable distance from town, on the president’s uncle’s
property. The uncle, sensing personal advantage, tried to leverage the sale of the
spring to the community. The president, citing the benefit of the community, threatened
to have the spring seized as property of the state (all surface water is public domain in
Honduras) and the uncle, thus angered, decided he would only sell the spring at an
outrageous price of more than the entire property was worth. The political will was not
sufficient to make the president’s stance any more than an idle threat, and the
community was left without a water source.
Sometime before the arrival of the author to El Caracol as Peace Corps Volunteer, the
president began negotiating with a man from the department capital who had purchased
a secondary property in the headwaters of the Caracol River. The man was willing to
“be a good neighbor” and assist the community with their search for a water source by
granting them access, free of charge, to the tributary of the Caracol River on his
property. A fellow Peace Corps Volunteer from the Water and Sanitation Project was
contacted to assess the topography and develop a design for the water system. The
volunteer would end up having to make three separate trips to the community with
surveying equipment to add households who belatedly were convinced of the viability of
the project and did not want to be left out.
Funding was promised by an NGO in the department capital (with funds from the
European Union for water projects to promote watershed management), contingent on
the submission of a proposal with all required legal documentation. When the author,
having assisted the water and sanitation volunteer in his third excursion, began to work
on the proposal it was discovered that the landowner did not in fact own the property as
35
he had not yet paid of the mortgage. Thus began a convoluted process of determining
if the bank could grant approval in his stead. During this time, community support for
the project waned in favor of a four community rural electricity project that was
beginning to gain momentum. The issue of bank approval was resolved several months
later, just as the owner had finished paying of the mortgage. He remained steadfast in
wanting to help the community, but was adamant that he needed to talk to his lawyer
before proceeding. In the meantime, men of the cadaster office of the municipality had
gone to the property to draft an official document granting access to a small zone in the
tributary for the purpose of the construction of a small dam and water intake.
Months later, in the subsequent meeting, the owner was no longer willing to sign a
document officially granting access to the community, but stated he was still willing to
help out the community in a more informal way. It is the opinion of the author that the
lawyer dissuaded the owner with the legal ramifications of providing a water source to
the community. The owner had stipulated that the dam must be below his building to
avoid risk of flooding, but a corral, several cow pastures, and an unimproved vehicle
stream crossing were all above the proposed dam intake location. It is likely that owner
did not wish to incur the potential responsibility for the health of the community with his
signature if the water source were to become contaminated. He said that the project
could still go through, maybe with a few less households incorporated, but he would not
be able to sign anything. As no NGO will grant funds for a project without legal basis,
the projected was effectively hamstrung. Nevertheless, by that time the promised
funding was no longer available as a result of the coup in June 2009 that disrupted
foreign relations and caused most foreign aid to be frozen or withdrawn. At the time
that the author completed his Peace Corps service in September 2010, the El Caracol
town council was considering the prospect of drilling a well with the potential arrival of
electricity to the community. However, only two of the four original communities had
obtained access to electricity at that time as funding for the rural electrification project
was rerouted for political reasons stemming from the coup.
Currently, the majority of households in El Caracol obtain water for drinking/cooking
from a single semi-improved spring on the south side of the River Caracol. Enclosed by
four cement walls and covered with a locked lid of wooden slabs, the spring is perceived
to be a better water source than open-air spring which served as the old community
water source mentioned in this study. In the rainy season, the location of the spring
poses a threat to residents on the north side of the river as water levels can rise with
little warning, and using the bridge to the west of the community more than doubles the
workload of the women and children tasked with carrying water to meet household daily
needs.
36
Appendix B: Precipitation data for El Caracol and La Rinconada, Honduras
Daily Precipitation Measured in Inches for El Caracol (G1) and La Rinconada (G2)
Date
1
Apr
G1
May
G2
G1
G2
Jun
Jul
Aug
Sep
G1
G2
G1
G2
G1
G2
G1
G2
1.05
0.5
0
0
0.15
0.1
0
2.15
0.3
0.1
2
0
0.1
0.4
0.3
0
0
0
0
0.6
0.25
3
0.5
1.5
1.4
0.6
0.05
0
0.4
0.4
0.7
0.4
4
0.1
0
0
0
1.3
1.7
0.7
0.5
0.5
0.4
5
0
0
0
0
0.5
0.7
1
0.9
0.2
0.2
6
0
0
0
0
0.6
0.5
0.9
1.2
0.6
0.5
7
0
0
0
0
0.2
0
0.1
0.1
0.5
0.4
8
0
0
0
0
1
1
0.05
0
0.1
0
9
0
0
0.2
0
0.15
0.5
0.75
0.9
0.7
0.2
10
0
0
0
0
0
0
0
0
0.3
0.3
11
0
0
0
0
0
0
1.5
1.1
0.3
0.3
12
0
0
0
0
0.6
0.9
0.4
0.3
2.9
2.2
13
0
0
0.3
0.3
0.2
0
0.1
0
0.2
0.2
14
0
0
0
0
0.2
0.2
0.15
0.3
0
0
15
0.2
0
0
0
0
0
1.3
2.7
0.6
0.5
16
0.15
0
1.1
0
0
0
0.05
0
0.1
0.1
17
0
0
1
1.1
1.5
2.2
0.7
0.9
0.5
0.7
18
0
2
0
0
1
1
0
0
0.2
0.3
19
0.25
0.2
0
0
0.05
0
1.4
1
3
1.8
20
0.05
0.5
0.3
0.4
0
0
0.3
0.4
21
0.25
1
0
0
2.7
2.9
0.9
0.6
22
0
0.9
1.6
0
0
0
0
0.25
0.6
23
0
1.3
0.6
0
0
0
0
1.5
1.6
24
0
0.3
0.05
0
0
0
0.5
0.7
25
0
1.45
0.6
0.8
0
0
0.9
0.8
2.6
2
0.2
0.1
0.2
1.9
1.6
0.5
1.2
1.5
0.1
0
0
0
2.1
2
0.8
0.5
0.25
0.3
3.1
2.2
0
0.4
12.15
8.85
1.9
26
0
0
27
0.8
2.2
28
0.9
2.6
29
1.1
2.95
30
1.1
0.95
0.9
2.5
1.9
22.6
14.25
31
Total
5.4
N/A
2.45
4.9
11.05
8.1
37
0.7
0
0
0.4
0.4
0.1
0
0.9
0.6
12.15
13.1
21.65
21.9
Appendix C: Precipitation data for San Marcos de Colón, Honduras
Monthly precipitation in inches for San Marcos de Colón, Honduras courtesy of the
Honduran Secretary of Natural Resources (SERNA)
year
Jan
Feb
Mar
Apr
May
1973
Jun
Jul
Aug
Sep
Oct
Nov
Dec
4.26
2.17
7.59
7.72
10.50
0.33
0.13
1974
0.11
0.02
0.09
0.02
10.89
7.43
1.17
3.87
14.24
5.11
0.19
0.42
1975
0.54
0.07
0.12
0.71
5.85
1.63
3.55
2.67
15.89
7.46
6.54
0.00
1976
0.27
0.19
3.92
5.31
7.70
0.69
0.97
3.63
13.89
1.04
0.28
1977
0.00
0.00
0.00
1.67
14.41
4.70
1.17
3.64
3.91
2.57
0.62
0.00
1978
0.02
0.02
1.61
0.36
9.18
2.81
5.11
1.69
6.96
1.97
0.41
0.62
1979
0.11
0.43
0.20
7.11
3.56
9.38
5.48
6.28
8.30
8.39
0.70
0.07
1980
0.00
0.00
0.00
1.31
12.37
5.74
5.19
3.72
7.79
13.09
3.15
0.13
1981
0.00
0.18
0.34
2.05
12.45
16.08
1.60
9.89
3.87
4.96
0.31
1.79
1982
0.52
0.73
0.48
1.99
14.06
10.13
0.94
1.00
5.59
4.42
2.96
0.12
1983
0.02
1.29
0.13
0.70
2.88
7.53
2.51
5.93
8.01
2.61
2.11
0.15
1984
0.32
0.07
0.60
2.34
5.88
7.50
8.76
7.57
13.73
3.32
0.63
0.31
1985
0.07
0.00
0.00
2.23
3.29
2.33
4.37
4.02
4.48
9.15
4.08
0.46
1986
0.09
0.45
0.00
0.00
17.35
2.80
3.13
5.93
2.99
2.82
0.83
0.13
1987
0.50
0.00
3.79
0.00
4.39
5.71
5.20
5.12
5.30
1.40
0.31
0.29
1988
0.10
0.20
1.94
3.43
7.55
7.70
3.48
14.25
15.12
6.40
0.57
0.19
1989
0.29
0.19
1.57
1.60
3.25
4.23
2.93
7.17
12.75
1.08
1.43
0.59
1990
0.00
0.00
0.00
0.47
5.54
1.33
2.87
3.35
3.19
9.09
4.91
1.44
1991
0.18
0.00
0.15
1.26
3.61
4.30
2.13
5.54
4.93
5.82
0.98
0.07
1992
1.15
0.89
0.08
0.57
16.69
2.78
0.00
0.46
1993
0.35
0.80
3.95
6.11
12.44
6.34
1.57
0.74
1994
0.55
0.13
0.83
1.69
1995
0.02
0.06
4.07
5.03
1996
0.30
0.21
0.07
1.52
1997
0.22
0.01
1.60
1998
0.01
0.00
1999
2.18
0.00
2000
0.34
2001
15.24
10.92
3.47
6.90
5.59
1.04
1.71
6.47
10.09
2.06
0.44
12.26
12.08
5.01
23.09
12.94
8.14
0.27
0.52
6.97
1.74
8.36
5.82
7.91
10.92
4.51
0.01
0.71
4.42
11.24
0.80
1.46
4.33
10.80
3.34
0.19
2.04
0.09
3.79
5.52
11.86
10.70
8.32
20.52
3.15
0.00
0.79
0.79
9.27
19.70
5.59
4.15
13.74
10.22
1.38
0.87
0.51
0.00
1.20
5.89
3.50
3.40
5.43
5.94
0.44
0.13
0.15
0.06
1.59
1.50
11.70
1.00
0.71
2.04
9.28
6.95
1.70
0.04
2002
0.11
0.01
0.08
0.24
10.10
7.19
2.93
1.85
1.57
11.20
9.63
0.29
2003
0.33
0.00
1.96
0.70
9.52
13.94
0.94
4.12
16.75
9.88
1.09
0.06
2004
0.00
0.01
0.01
0.81
1.65
8.10
3.50
2.26
12.03
3.89
0.91
0.00
2005
0.00
0.00
0.50
0.31
13.36
16.15
11.22
6.21
7.20
10.79
1.42
0.82
2006
0.60
0.01
0.01
3.80
7.87
5.84
3.81
4.61
7.76
2.07
0.38
2007
0.11
0.14
0.24
2.09
8.99
5.29
1.93
12.38
9.06
19.44
0.83
0.12
2008
0.06
0.94
0.58
1.43
5.93
7.69
11.08
10.59
6.18
13.62
0.02
0.11
2009
0.39
0.00
0.00
0.00
11.93
16.50
4.06
0.35
4.28
2.15
2.59
1.79
2010
0.01
0.00
0.71
3.11
13.23
8.83
13.56
31.86
21.18
6.04
0.72
0.00
38
3.74
Appendix D: Water Depth Measurements
Water depth measurements in inches used for weir discharge calculations.
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
May
spring
river
Jun
spring
river
0.375
1.25
1.75
1.875
1.5
0.3125
0.375
0.3125
0.3125
0.375
1.25
1.375
Jul
spring
1.375
1.25
1.0625
river
1.375
1.125
1.4375
1
0.875
0.875
0.8125
0.75
11
0.625
10
0.625
9.5
0.5
1.25
17
1.625
23
1.0625
15
0.9375
10.5
2.125 too high
1.1875
13
1
12
0.875
11.5
0.75
10
0.8125
9.5
0.75
11.5
0.75
10
0.5
10
0.5
9
0.625
9
39
Aug
spring
river
0.5
0
0
0.9375
1.25
0.875
0.875
1
0.75
1.25
1.125
1
0.75
1.25
1.0625
1.0625
1
1.375
7.5
8
13.5
14
16.5
15
1.25
1.125
1.3125
1.25
1.25
1.125
1.1875
1.5
1.4375
1.25
1.1875
16
16.5
19
19
18
15.5
19
36
24.5
19.5
21.5
16
12
19
18
14.5
13
17
14
15
13
18.5
Sep
spring
river
0.9375
17.5
1.125
23
1.0625
23.5
0.9375
20
1
0.875
1
0.9375
17.5
15.5
15.5
14
0.9375
0.875
16
15.5
14
14
Appendix E: Timed Trials of Discharge from Hose Draining Spring
Time to fill 3 liters recorded in 3 separate trials for discharge calculations.
Date
7/29/2010
7/30/2010
7/31/2010
8/2/2010
8/3/2010
8/4/2010
8/5/2010
8/6/2010
8/7/2010
8/8/2010
8/9/2010
8/10/2010
8/11/2010
8/12/2010
8/13/2010
Time to 3L (s)
44
46
48
43
46
46
not flowing
not flowing
42
43
43
42
47
46
not flowing
33
39
40
47
51
50
not flowing
38
41
41
39
43
42
not flowing
not flowing
not flowing
Date
8/14/2010
Time to 3L (s)
44
47
47
not flowing
not flowing
36
41
41
not flowing
not flowing
not flowing
not flowing
not flowing
not flowing
not flowing
not flowing
46
48
47
not flowing
39
37
41
44
42
41
41
43
42
36
39
40
8/15/2010
8/16/2010
8/17/2010
8/18/2010
8/19/2010
8/21/2010
8/22/2010
8/23/2010
8/24/2010
8/25/2010
8/26/2010
8/27/2010
8/28/2010
8/29/2010
8/30/2010
8/31/2010
9/1/2010
40
Date
9/2/2010
9/3/2010
9/4/2010
9/7/2010
9/8/2010
9/9/2010
9/10/2010
9/14/2010
9/15/2010
9/16/2010
Time to 3L (s)
44
45
46
41
45
46
45
48
49
45
48
49
51
54
58
53
52
52
51
56
55
56
66
66
57
63
66
59
65
65
Appendix F: River Cross Section and Equal Area Approximations
41
Appendix G: Thornthwaite Mather Water Balance Equations
Equations inherent to the water balance calculations as adapted from Shonsey (2009):
𝐼𝑓 𝑃𝑚 ≥ 𝑃𝐸𝑇𝑚 𝑡ℎ𝑒𝑛 𝐸𝑇𝑚 = 𝑃𝐸𝑇𝑚 ; 𝑏𝑢𝑡 𝑖𝑓𝑃𝑚 < 𝑃𝐸𝑇𝑚 𝑡ℎ𝑒𝑛 𝐸𝑇𝑚 = 𝑃𝑚 − ∆𝑆𝑂𝐼𝐿𝑚
∆𝑆𝑂𝐼𝐿𝑚 = 𝑆𝑂𝐼𝐿𝑚 − 𝑆𝑂𝐼𝐿𝑚−1
𝑆𝑂𝐼𝐿𝑚 = 𝑆𝑂𝐼𝐿𝑚−1 �exp �−
Where:
𝑃𝐸𝑇𝑚 − 𝑃𝑚
��
𝑆𝑂𝐼𝐿𝑚𝑎𝑥
𝑆𝑂𝐼𝐿𝑚𝑎𝑥 = 𝜃𝑓𝑐 𝑍𝑓𝑐
Pm = Monthly precipitation (mm)
PETm = Monthly potential evapotranspiration (mm)
ETm = Monthly actual evapotranspiration (mm)
ΔSOIL = Monthly change in soil moisture (mm)
ΔSOILm = Present month’s estimated soil moisture (mm)
ΔSOILm-1 = Previous month’s estimated soil moisture (mm)
ΔSOILmax = Maximum achievable soil moisture (mm)
θfc = Field capacity of root zone (mm)
Zfc = Vertical extent of root zone
With ΔSOILm-1 equal to ΔSOILmax for the starting calculation
Potential evapotranspiration as calculated by the Hamon method (Dingman 2002):
Where:
𝑃𝐸𝑇 = 924𝐷
𝑒𝑎∗ (𝑇𝑎 )
𝑇𝑎 + 273.2
PET = potential evapotranspiration (mm/month)
D = Day length (hr)
e*a = saturation vapor pressure at mean daily temperature (kPa)
Ta = mean daily temperature (°C)
42
Saturation vapor pressure is approximated as (Dingman 2002):
𝑒𝑎∗ (𝑇𝑎 ) = 0.611𝑒𝑥𝑝 �
17.3𝑇𝑎
�
𝑇𝑎 + 237.3
Day length is calculated as (Dingman 2002):
𝑐𝑜𝑠 −1 [−𝑡𝑎𝑛(𝛿)𝑡𝑎𝑛(Λ)]
𝐷 = 2�
�
𝜔
Where
𝛿 = 0.006918 − 0.399912𝑐𝑜𝑠(Γ)
+ 0.070257 sin(Γ) − 0.006758 cos(2Γ) + 0.000907 sin(2Γ)
− 0.002697 cos(3Γ) = 0.00148sin(3Γ)
Γ=
2𝜋(𝐽 − 1)
365
Γ = day angle (radians)
J = day number (Julian days)
δ = sun declination (radians)
Λ = latitude (radians)
ω = earth’s angular velocity (0.2618 radians/hr)
43
2010
www.worldweatheronline.com
0
:
44
121
-121
0
-3
3
0
Potential Evapotranspiration, PET:
Net W ater Input, RAIN + MELT - PET
Soil Moisture, SOIL:
Change in Soil Moisture, /\SOIL:
Actual Evapotranspiration, ET:
Recharge & Runoff, RAIN+MELT-ET-/\SOIL:
0
0
Snow Melt, MELT:
W ater Input, RAIN+MELT:
0
0
Precipitation as Rain, RAIN:
0
1.00
Melting Factor, F:
Snow Pack, PACK:
26.5
Mean Monthly Temperature, T:
Precipitation as Snow, SNOW :
0
J
Monthly Precipitation, P:
Month:
11.3
Day Length, D (hr):
0
0
0
0
0
-135
135
0
0
0
0
0
1.00
28.0
F
11.6
-0.232
0.757
0.241
-0.371
45
15
F
12.3
0.165
1.790
105
A
12.8
0.406
2.840
166
J
0.23
J
12.7
0.377
3.365
196.5
rad
W ATER BALANCE
12.6
0.328
2.315
135.5
M
12.5
0.247
3.899
227.5
A
12.1
0.058
4.424
258
S
:
:
11.7
-0.147
4.949
288.5
O
0
m ax
SOIL
SOIL
0
0
0
0
0
-139
139
0
0
0
0
0
1.00
28.0
M
0
137
0
0
-2
139
137
0
0
0
137
1.00
27.5
137
A
335
139
100
100
435
139
574
0
0
0
574
1.00
27.0
574
M
144
137
0
100
144
137
281
0
0
0
281
1.00
26.5
281
J
165
144
0
100
165
144
309
0
0
0
309
1.00
27.5
309
J
405
145
0
100
405
145
550
0
0
0
550
1.00
28.0
550
A
381
123
0
100
381
123
504
0
0
0
504
1.00
25.5
504
S
0
0
68
-68
32
-116
116
0
0
0
0
0
1.00
25.0
O
:
0
22
-22
10
-119
119
0
0
0
0
0
1.00
26.0
N
0
11.4
-0.319
5.474
319
N
1
100
rz
Temperatures in degrees Celcius , W ater-balance terms in mm water equiv alent.
11.9
-0.039
1.265
74.5
M
0 mm (water equivalent)
Day Angle, Γ (radians):
J
Declination, δ (radians):
Julian Day, J :
Month:
Previous December Snowpack, PACK
0.20
decimal degrees
Soil Field Capacity, θ f c :
Latitude: 13.394
Root Zone Depth, Z
Titles, Labels, and Units (Protected)
Pers onal Precipitation Meas urements
Computed Values (Protected)
Location of Climate Data: El Caracol, Honduras
Y ear:
Data Source:
Cell Color Codes: Input Data
0
0
7
-7
3
-117
117
0
0
0
0
0
1.00
26.0
D
11.2
-0.406
5.999
349.5
D
mm
mm
500
1429
925
0
45
782
1572
2354
0
0
0
2354
1
27
2354
Annual
12
Average
mm
See Box 7-3. PET computed via Hamon equation [Eqn.( 7-63)].
THORNTHW AITE-TY PE MONTHLY W ATER-BALANCE MODEL
Based on a spreadsheet titled, "ThornEx.xls," by S.L. Dingman, Physical Hydrology, 2nd Ed.
Appendix H: Thornthwaite Mather Water Balance Model Results
Appendix I: Delineated Watersheds
Figure 8.1 Watersheds in the area of El Caracol as delineated using ESRI ArcGIS Desktop 9.3. The blue
polygon represents the topographic watershed of the old community water source spring. The red
polygon denotes the sub-watershed of the Caracol River upstream of the point where measurements
were recorded. The green polygon depicts the watershed of the Comalí River (at a point upstream of San
Marcos de Colón), of which the Caracol River is a tributary.
45
Appendix J: Regional Scale Lineament Interpretation
46
Appendix K: Coincidence Raster
Figure 8.2 Coincidence raster shown along with field mapped lineaments and springs. Watershed
boundaries are included for reference. The minimum coincidence for the raster was set at 4
according to the methodology of Bruning et al. (2011) to assure that coincidence was not the
result of a single image (ASTER and Landsat images have three interpretations). The coincidence
raster is compiled from the lineament interpretations with a 200 m buffer (100 m each side). A
buffer of 100 m and a pixel size of 50 m were used in creating the raster to increase coincidence
for the NW trending feature in the Caracol River watershed as the feature was mapped in all
interpretations but not in an exact location.
47