POPOV Yuriy - Riversymposium

ENVIRONMENTAL FLOWS FOR FIGHTING AGAINST DESERTIFICATION
IN RIVER DELTAS
Yu. M. Popov1, V. M. Starodubtsev2
1-Ecotera Ltd., 115 Jheltoksan st., of. 304, 050000, Almaty, Kazakhstan, [email protected]
2-National Agricultural University, 15 Geroiv Oborony st., Kiev, Ukraine.
[email protected]
Desertification of soils in the river deltas of arid regions becomes the largest ecological,
economic and social problem. Intensive flow regulation of the large rivers leads to deep
degradation of landscapes in their deltas on the area of many millions hectares. It is especially
noticeable at creation on the rivers of the large reservoirs or their cascades and intake of significant
amount of water for irrigation and industrial and communal supply.
Soil degradation extent and its character in deltas are defined mostly by intensity of river
flow regulation, climatic conditions and geomorphological features of deltas. On the basis of longterm researches and use of a considerable amount of space images we will try to typify soil cover
changes in deltas depending on the specified factors. Character of river flow regulation (seasonal
or long-term) and its intensity determine decreasing of water inflow in deltas, weakening of flooding
of hydromorphic soils, lowering of groundwater level, increasing of river water mineralization,
reduction of suspended solids inflow. So, in the rivers Syrdarya , Chu, Amudarya, Colorado, Huang
He, Euphrates water inflow to deltas decreased in the end of the past - in the beginning of current
century for 70-100 %, that is periodically they dried up in the lower reaches. The water
mineralization (salt content) for the same period increased in these rivers for 2-4 times. It led to a
basic change of water and salt regimes of delta’s soils and their fast degradation. As a whole in the
arid climate conditions there are processes of desertification, salinization and eolian destruction in
delta soils.
Depending on geomorphological conditions catastrophic degradation processes occur, first
of all, in continental deltas when the rivers do not run into reservoirs, for example, the river Chu in
Kazakhstan, Okavango - in Africa and others. Powerful degradation processes occur in deltas of
the rivers which run into lakes and internal seas, for example, the river Ili in Kazakhstan (Fig. 1),
Syrdarya and Amudarya - in the Central Asia.
Figure 1. The Ili River basin
(1- plains; 2 – inter-mountain valley; 3 – foothills; 4 – water area; 5 – mountains).
On soil degradation processes a reduction of suspended solids inflow of regulated rivers
essentially influences. And in deltas it leads to concentration of water flow into one or several basic
river channels and to reduction of hydromorphic soil areas (delta of the river Ili, etc.).
Unique real way of landscape degradation processes prevention or weakening in deltas of
regulated rivers is realization so-called «environmental flow» of waters in lower reaches.
Experience such flow increase has been accumulated in many transboundary river basins of the
Central Asia, America, China, Ukraine and other regions. But in all cases such practice faces
limitation of water resources. Therefore for flooding of deltaic landscapes it is necessary to use
effectively also returnable waters from irrigated fields, from the industrial and municipal enterprises
though they usually have poor quality and require clearing. There are also problems of the
coordination of volumes of such artificial high waters with interests of fish economy, electricity
generation and others. Long-term practice also shows that it is impossible to rely only on natural
water distribution of artificial high waters for flooding of deltaic landscapes. In some cases special
hydraulic engineering constructions and so-called “liman” (estuary) irrigation of natural delta
grasslands are necessary.
In delta of the river Ili desertification processes are connected with a construction of the
large (28 km3) Kapchagay water reservoir in the middle stream, and also intensive development of
irrigation in China and Kazakhstan. Soil and delta’s landscapes researches were conducted in
1968 - 2 years before the Kapchagay construction, and then they were carried out in 1972, 1977
and the next years. These researches had shown that designed environmental flow from the
Kapchagay to delta in amount of 1.25 km3 had not given expected result. Inflow of river water to
delta had essentially decreased (Fig. 2). Seasonal distribution of a runoff (Fig. 3) became adverse
for a delta flooding. The solid flow accumulated in the reservoir (Fig. 4).
Figure 2. Long-term changes in water flow of the Ili River.
Figure 3. Long-term and seasonal distribution of the water discharge in the Ili River.
Figure 4. Long-term and seasonal changes in suspended solids in the Ili River.
Soil and vegetation covers were promptly desertificated. It was allowed to predict a condition
of soil cover for 2000 (Table 1 and Fig. 5), showing fast growth of desertificated and saline soils
(Fig. 6).
Figure 5. Water regime of hydromorphic soils in the Ili River delta at desertification.
Soil indexes: Am – alluvial-meadow, Sm – swampy-meadow, Ms – meadow-swampy, S –
swampy, Tl – takyr-like soils, Sn – sands loose and poorly fixed, Sk – solonchaks (saline soils).
Texture of soils: 1 – clay and heavy loam, 2 – loam, 3 – light loam, 4 – loamy-sand, 5 –
sand.
Forms of moisture in soils: 6 – free water, 7 – TMC-CMC (total moisture capacity – capillary
moisture capacity), 8 – CMC-FMC (capillary water capacity – field moisture capacity). 9 – FMCCBMC (field moisture capacity – capillary-break moisture capacity), 10 – CBMC-WMC (capillarybreak moisture capacity – wilting moisture capacity), 11 – less WMC (wilting moisture capacity or
wilting point).
Table 1
Soil area changes in the Ili River delta at desertification (thousands of ha).
Soil
indexes
Аt
Аm
Аmdr
Аmdes
Sm
Smdr
Smdes
Ms
Msdr
Msdes
S
Sk
Tl
Sn
L
Total
Soils
Alluvial-meadow tugai
Alluvial-meadow
Alluvial-meadow dried
Alluvial-meadow desertificating
Swampy-meadow
Swampy-meadow dried
Swampy-meadow desertificating
Meadow-swampy
Meadow-swampy dried
Meadow-swampy desertificating
Swampy
Solonchaks
Takyr-like soils
Sands
Lakes
Years of survey
1968
1977
28.3
29.9
25.5
32.3
10.7
139.6
112.4
32.7
29.7
12.0
14.1
1.9
20.9
122.8
70.4
23.6
15.4
10.2
73.8
49.7
67.9
143.9
51.0
87.0
276.8
282.4
119.7
65.7
Predict
2000
30.4
46.3
21.9
62.6
25.2
16.3
40.1
7.3
18.1
28.4
205.9
158.8
294.2
20.1
975.6
975.6
975.6
Figure 6. Prognostic schematic soil map of the Ili River delta
(1 – sands in a combination with desertificating soils, sands in a combination with hydromorphic
soils, 3 – saline soils, 4 – takyr-like soils, 5 – desertificating soils, 6 – alluvial-meadow tugai soils,
7a – alluvial-meadow soils, 7b – alluvial-meadow dried soils, 8a – swampy-meadow soils, 8b –
swampy-meadow dried soil, 9a – meadow-swampy soils, 9b – meadow-swampy dried soils, 10a –
swampy soils, 10b – swampy dried soils, 11 – lakes).
But in 80s filling of the Kapchagay reservoir had been suspended and environmental flow to
delta were increased. And in 90s (after disintegration of the USSR) water consumption had sharply
decreased for irrigation in the Kazakhstan part of basin. All it was allowed to weakening, and even
suspends, degradation processes in delta, especially in the area of river-beds Zhidely, Kugaly, Ir
(Fig. 7).
Figure 7. Zoning of the soil cover changes in the Ili River delta in 2002.
1-Wetlands; 2-Soil drying-up & salinization; 3-Soil drying-up, desertification & salinization; 4Wetlands desertification & salinization; 5-Soil desertification & salinization; 6-Coastal wetlands; 7Desert soils of the ancient delta.
But landscapes of the left wing of delta were irreversibly deserted because of essential
reduction of runoff along streams Topar and Balatopar, and also along the basic river-bed Ili. In
perspective, however, river flow reduction of the Ili is expected in connection with irrigation
development in the Chinese part of basin, and also a restoration of earlier irrigated areas in
Kazakhstan. Therefore for preservation unique hydromorphic delta landscapes it is necessary
application of all measure complex for protection, rational use of water and soil resources in all
basin, and also optimization of a runoff distribution in delta (so-called Integrated Water Resources
Management).
In 60s of last century conditions for even more grandiose ecological accident in the Aral Sea
basin, having also a huge social consequences were created. Namely after 1960 irrigation scheme
construction in basins of the rivers Syrdarya and Amudarya was intensified. By 1970 the irrigated
areas here had reached 7 million hectares. The total water inflow of these rivers to the Aral Sea
has decreased by 9 km3 per year. By 1975 of the irrigated areas amounted already 6 million
hectares and runoff of the rivers in the Aral Sea had decreased for 15 km3 per year.
But the real ecological accident had burst in 80s of the last century when in the summer the
runoff of the rivers Syrdarya and Amudarya in the Aral Sea completely stopped. At a boundary of
21 century inflow of river water to the Aral Sea has decreased already approximately for 48 km3 per
year. As a result in deltas of the rivers Syrdarya and Amudarya already in 70-80ts fresh floods had
practically stopped, and prompt desertification of hydromorphic landscapes, degradation of soil and
vegetation covers had begun.
Periodic mapping of the Syrdarya river deltas (Fig. 8) visually shows, how powerful and fast
were this processes. And our forecast, made on the basis of long-term soil researches, has allowed
to present soil cover on the most delta part deserted, salted, with degraded xeromorphic and
halomorphic vegetation and separate rice fields among solonchaks.
Space images have allowed to estimate reliability of the forecast (Fig. 9). It has been based
on results of land researches. Also some changes took place last decades in connection with
reduction of the irrigated areas and application of special environmental flow. Desertification
processes has weakened in head and middle parts of delta; however it has not changed their
general orientation in the peripheral (near mouth) part. But appreciable improvement of ecological
conditions has occurred along old river-bed Kuvan-Darya. The river waters were specially directed
for flooding of hay, pastures and tugai forests.
It is important to notice also, that last decade powerful winter flow allowances to the
Syrdarya delta from the Toktogul reservoir were carried out. They caused flooding of the large
areas in present-day and ancient deltas (Fig. 10). The considerable areas of hydromorphic (near
river-bed) delta landscapes are flooded. However these environmental flow have serious
destructive action on settlements and economic objects in all Southern Kazakhstan.
Desertification processes in the Amudarya delta as a whole are similar to that in the
Syrdarya delta. But they are shown most sharply in the peripheral delta part adjoining the Aral Sea.
Figure. 8. Soil area changes in the Syrdaria River delta.
Figure 9. Syrdarya Delta:
1-Soil drying up & salinization: 2-Soil desertification & salinization: 3-Soil drying up, salinization &
desertification; 4-Meadow soil restoration; 5-Soil salinization & desertification; 6-Desert grey-brown
soils; 7-Salty-sand desert formation on the Aral Sea bottom.
Figure 10. Winter flooding in the Syrdarya Delta.
Delta zoning of 2002 (Fig. 11) has shown, that environmental flow here have been directed
to small reservoirs in the so-called «a protective belt». This belt is contiguous with drying bottom of
the Aral Sea. The ecological effect of such environmental flow has appeared doubtless. However,
comparison to the space image of 2008 (Fig.12) has shown, that the deserted delta part has
increased. Moreover, space pictures have shown how promptly the desertification area in the
Syrdarya and Amudarya deltas has been extended at the expense of drying bed of the Aral Sea.
The huge salt and sandy desert became a powerful source of wind carrying over of salts and dust
to adjacent territories, worsening both ecological, and social conditions on them (Fig. 13, 14).
Figure 11. Amudarya Delta.
1-Soil drying up & partly salinization; 2-Soil drying up, desertification & salinization; 3-Soil
desertification & salinization; 4-Soil salinization & desertification, with artificial water bodies; 5Sandy desert on the Aral Sea bottom; 6-Salty desert on the bottom; 7-Water area.
Figure 12. Amudarya Delta. 2008 (VI-28).
Figure 13. The Aral Sea. Salt and dust transfer by the wind on the adjacent territory.
Figure 14. Ships on the drying-up bed of the Aral Sea.
Experience of fighting against desertification in the river Heihe delta (the western China)
where for last decade degraded processes have been essentially weakened is very indicative
(Fig15).
Figure 15. Heihe Delta. 2008 (VI-16).
Thanks to the whole complex of water security measures called as Integrated Heihe River
Basin Management, water has returned again to the most remote parts of the chain of deltaic
enlargement. For this purpose normalization of water intakes was entered in the top, middle and
bottom parts of basin. Reconstruction of irrigation schemes and the main channels has been
carried out. The payment for using water for all economic branches has been entered. All it has
allowed by means of environmental flow to delta partially to revive the local ecological systems.
The large environmental interest is caused by a situation in the river Colorado delta on the
border of the USA and Mexico. The irrigation of the huge areas in the Imperial Valley in the USA
has caused powerful desertification and delta soil salinization of this river. And only in the last time
environmental flow to delta in amount nearby 1 km3 of river water are carried out. Also salty waste
waters from irrigated fields are directed to the lowering Cienega de Santa Clara where
hydromorphic landscapes are formed. The newest space pictures of this region show (Fig. 16), that
these measures it is possible to restore hydromorphic landscapes (wetlands) only in a narrow strip
along the river-bed of the Colorado and in the named bogged up and salted lowering.
Figure 16. Colorado Delta. 2008 (IV-24).
And at all drama "revival" of hydromorphic landscapes due to flow allowances of river
waters was noted in a some last years in lower reaches of the Mesopotamia rivers (Euphrates,
Tigris). On an extent of decades intensive hydraulic engineering construction and irrigation
development in the top and middle reaches of the Euphrates and Tigris caused the most powerful
desertification of huge territory in the lower reaches. Even recently well-known hydromorphic
landscapes at merge of the rivers Euphrates and Tigris by 2001 had completely dried up, salted
and degraded (Fig. 17).
Figure 17. Mesopotamia 2001 (XI).
But destruction of Iraq economy owing to the war had led to increase of water flow in lower
reaches and to partial restoration of these hydromorphic landscapes (Fig. 18).
It is obviously, that such condition of these landscapes cannot be considered as a steady,
and it is necessary to develop an action system for protection and rational use of water and soil
resources in all basin. It is especially necessary to protect hydromorphic landscapes of deltaic
area.
Figure 18. Mesopotamia 2008 (V-24).
As a whole it is necessary to notice, that struggle against desertification in deltas of the
rivers with regulated flow has already got considerable practical experience. Concrete results in
technology of environmental flow applications, distributions of river water in deltas have been
reached. But at present time this experience is obviously insufficient. And abundantly clear, that
struggle against desertification in deltas can be carried out only on a basis of the basin analysis of
water and land resources usage, reconstruction of irrigating systems, including basin irrigations,
revision of all strategy of economy development in such basin.
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