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Chapter 23. Some aspects of the necessity and feasibility of China's proposed south-to-north water transfer
Yao Bangyi and Chen Chunhuai
Planning and Management Office, Ministry of Water Conservancy Beijing, China
THERE ARE MANY divergent views on the necessity and feasibility of the proposed south-to-north water transfer in China. The fact that water is deficient in North China is obvious to all. Whenever there is a drought year agricultural yields fall over large areas. In Tianjin and Cangzhou, where water is the most deficient, there is a water crisis even in normal years. Nevertheless, some people hold the opinion that this shortage can be overcome by using local water resources rationally or by relying on the water of the Huang He for relief. Others feel that the proposed large transfers are necessary but feel that prudent consideration should be given to the problems of economic efficiency and environmental impacts. Although many people have studied these problems, further work is needed to provide a more penetrating analysis. This paper raises some views on several aspects which have been discussed and gives opinions regarding certain problems which need to be dealt with in further arguments over the necessity and feasibility of northward water transfer.
ON THE NECESSITY OF THE PROPOSED SOUTH-TO-NORTH WATER TRANSFER
The plans to divert Chang Jiang water to northern Jiangsu and Han Jiang water to southern Henan have already begun to be implemented. What we stress here is the problem of diverting water from the basin of the Chang Jiang into the Hai He basin north of the Huang He.
If We Thoroughly Utilize the Local Water Resources in the Hai-Luan Basin, is it Still Necessary to Import Water from Other Basins?
The average annual volume of runoff in the Hai-Luan basin is 28.3 km³, only 2,500 m³/ha of cultivated land, far less than China's other major river basins (see Yao Bangyi and Chen Qinglian, Chapter 9). This precious surface runoff should be utilized fully, but one problem which merits study is what is the optimal level of utilization, given the specific conditions of the river basin?
Since the 1950s a large number of reservoirs and irrigation have been built in the Hai basin. These began to come into play one after the other in the late 1960s, causing a marked reduction in the discharge into the sea in average or dry years. For example, in the dry year of 1968, only 1.0 km³ flowed into the sea, while in 1952, a year of similar runoff, the volume discharged amounted to 5.4 km³. In wet years, less water is used for irrigation and the flow into the sea has not decreased by very much.
Consequently, it is misleading to use the average annual discharge into the sea to show that there is still some surface runoff available for utilization. In fact, the rate of utilization of surface runoff in the Hai basin is already rather high and most of the relatively large and economically worthwhile reservoirs with good control conditions have already been constructed. The small number of reservoirs which could still be built would not increase the utilization of runoff by very much.
The coefficients of variation for precipitation and runoff are large, and the disasters of flooding, drought, salinization and sedimentation coexist in the basin, requiring the discharge of a considerable amount of surface runoff, including floods and surface water in excess of the storage capacity, drainage to improve salinized soil, and the regular discharge in the lower reaches which is necessary to prevent sedimentation of the estuary and ensure an appropriate environment for the survival of littoral aquatic life. Therefore, even if it were technically possible to use the greatest part of surface runoff in the Hai He basin for industrial, agricultural and municipal uses, it would not be economical, nor would it be environmentally permissible.
Rapid progress has been made in the exploitation and utilization of the groundwater in the Hai He Plain in the past dozen or so years. In many places the intensity of extraction of water from the deep aquifers has greatly exceeded the recharge capacity, causing the water table to descend over a large area, bringing about serious consequences such as increases in pumping costs, deterioration of water quality and land subsidence. Due to the inadequacies of recharge conditions, most people hold that the deep groundwater cannot serve as the main source of water for industry and agriculture.
Different estimation methods have led to quite disparate results in calculating the amount of usable shallow groundwater, so further discussion, testing and verification are necessary. Some calculations do not take sufficient account of the double counting of a portion of groundwater which also appears as surface water, so we cannot use them to make a direct estimate of total water resources (see Li Jiasan, Chapter 16). Other estimates are based on too large a regionalization and pay insufficient attention to the spatial and temporal variations in shallow groundwater, providing relatively optimistic figures based on average conditions. These numbers are insufficiently reliable and do not provide a suitable basis for planning. Precipitation is the main source of shallow groundwater recharge. The magnitude and distribution of precipitation directly affect the amount of recharge. In general, the smaller the recharge in a given year, the greater is water use. Average values do not reflect this.
The soil layer of the Hai He plain is thick, with many favourable conditions for storage of water due to the alternating erosion and sedimentation of the tributaries of the Huang He and Hai He. Some people have envisaged using the tremendous underground storage capacity of the soil interstices to store surface runoff and reduce groundwater evaporation through controlling the water table, thereby increasing the degree of water utilization (see Wu Chen and Wu Jinxiang, Chapter 21). There are numerous problems in carrying out this idea which must be studied, including the following aspects:
(1) It is hard for surface reservoirs to avoid discarding
water because of their multipurpose tasks, such as flood and
irrigation. Similarly, underground reservoirs would have to
discard water as a part of their operation when they take into
account the different kinds of control requirements for drought,
flooding and salinization on the plain. If we only heed storage
but not drainage, the lesson we have learned in the past is that
this will lead to serious harm.
(2) About two-thirds of the plain is cultivated. Maintaining a certain amount of soil moisture in the cultivated layer is a necessary condition of crop growth. Hence water loss through evaporation is inevitable. If the water table is lowered, reducing evaporation of phreatic water, the groundwater recharge might be increased somewhat, but irrigation requirements would increase, partially offsetting the greater abundance of groundwater.
(3) When the phreatic water level is relatively low, a small amount of precipitation can only moisten the surface soil and then be consumed in evaporation without recharging the groundwater. Consequently, the effects of underground storage on atmospheric precipitation and surface runoff can only be determined after being studied concretely in the course of project planning.
The above aspects show that although there is still some potential for using local water resources in the Hai-Luan basin, if we are to tap that potential we must consider technical, economic and environmental feasibility. It is therefore inadvisable to overestimate this potential. As with other natural resources, the estimation of water resources should be done carefully, leaving a margin for error. In our opinion, the potential is limited and we must actively study measures for transferring water from other basins.
If We Restrict Water Use and Further Promote Economizing of Water, is it Still Necessary to Import Water From Other Basins?
Agriculture is the largest user of water in the Hai He basin. At present there is some waste in water use in surface irrigation districts, with a canal system utilization factor below 0.4. If we assume that the necessary technical and management measures are adopted to raise the utilization factor, can the irrigated acreage be expanded correspondingly? The rate of guaranteed supply in some irrigation districts is quite low. Reducing the level of waste in these cases can only increase the rate of guaranteed irrigation with no room left over for expanding the irrigated area. Some of the overflow of irrigation districts in the upper reaches is intercepted and used by downstream districts, so it is very hard to calculate the amount of waste from an overall point of view. The seepage water of some surface irrigation districts is in actuality a recharge source for the groundwater of downstream or neighbouring well irrigation districts. If we look at the drainage basin as a whole, we are far from able to satisfy all of the requirements of farm irrigation by relying on economizing of water.
At present, industry wastes water. Much water which could be reused is not reused. Even more wasteful is the pollution of water bodies by industry. Some industrial and municipal waste water is used for field irrigation, but some cannot be used. Whether viewed from the angle of environmental protection or from the rational utilization of water resources, the problem is the purification of industrial and municipal waste water. While some water can be saved in this way, we must also note that the present level of industrial development is far from high in the Hai He basin. With further industrial development and improvements in the standard of living of the people, there will be a large increase in the basin's industrial and municipal water use, even if we take full account of waste water resource difficulties in our development planning and do not set up industries which consume large amounts of water. The rate of guarantee of industrial and municipal water use is high so we must search out reliable water sources. Some coastal industries may also study the desalinization of sea water as a means of solving their water source problems.
To sum up, every possible means must be taken to save water in the Hai He basin and make complete use of existing water resources, but we should have sober estimates of the total effectiveness of economizing. In view of the technical, economic and management conditions which can be attained in the near future, the local water resources cannot satisfy the water use requirements of the entire basin by solely relying on restricting water use and economizing. In particular, due to the uneven spatial distribution of water resources, some areas such as the eastern Hai He plain have no water to save during a drought year.
Transferring Water From the Huang He to Help Out the Hai He
In its lower reaches, the Huang He is an accumulational channel whose bed is higher than the Huai He plain in the south and the Hai He plain in the north. The topography would allow the water of the Huang He to flow by gravity to virtually the entire Hai He plain. Projects to divert the Huang He waters to irrigate the Hai He plain have been constructed since the early 1950s and the area so irrigated has grown to over 670,000 ha (10 x 106 mou). This area could be enlarged further by completing the entire conveyance system to the fields and strengthening irrigation management, but there are two problems which must be solved before water is diverted from the Huang He:
(1) Estimates of the Huang He Water Conservancy Commission
indicate that prospects are not very bright that water will be
available for diversion in the lower reaches of the Huang He. In
the 1950s, 48 km³/annum flowed into the sea, but by the 1970s
this had fallen to less than 30 km³/annum, most of it occurring
during the flood season. During April, May and June, when the
irrigation requirements are the greatest, the average discharge
into the sea is only 3.5 km³. It fell to a mere 0.3 km³ in the
lowest flow year of 1978, when the flow ceased altogether several
times during the peak water use period. A certain amount of
discharge is necessary for sediment transport and to satisfy
ecological demands in the estuary. We can anticipate that there
is little possibility of increasing the amount of water diverted
from the Huang He during the irrigation season. Moreover, during
the flood season when there is more water, its sediment content
is extraordinarily high and the period of high flow is
concentrated, presenting numerous technical difficulties to
utilizing these waters effectively.
(2) The Huang He is known world-wide for its large sediment content. The diversion irrigation districts in its lower reaches have some practical experience in dealing with the silt problem. For example, saline lowlands adjoining the river are used as settling basins and the clear water is then drawn off for irrigation, thus killing two birds with one stone. Good results have been obtained using this method along stretches with appropriate conditions, but these conditions are not available everywhere. None of the diversion irrigation districts have found a method which is effective and which can handle the sediment problem over a long term. Finding a solution becomes even more difficult when the water of the Huang He is sent over a long distance.
If we are to enlarge the scope of diversion from the Huang He onto the Hai He plain, a practical scheme would be to make use of the relatively sediment-free surplus water of the Huang He during the non-irrigation period of the winter. If the sedimentation and storage problems can be solved properly, we can meet the urgent needs now present in some seriously water deficient areas.
To sum up, there is a certain potential in making fuller use of local resources in the Hai basin, in paying greater attention to conserving water and increasing diversions from the Huang He. How to tap this potential is something which requires concrete analysis. Nonetheless, the results of studies which have already been done in various fields show that our ability to unearth more potential from local water resources is not sufficient to negate the necessity of transferring water from the Chang Jiang.
ON THE FEASIBILITY OF THE PROPOSED SOUTH-TO-NORTH WATER TRANSFER
In studying the feasibility of the proposed south-to-north transfer in an allround way we must consider three aspects: engineering technology, economics and environmental effects. With the experience China has already gained in hydraulic construction, there are no insurmountable difficulties in engineering technology. What we must continue to work on in this area is to improve our technological level. The economic and environmental aspects have not yet been studied in sufficient depth. Differences in views on the feasibility of the proposed transfer tend to concentrate on these two aspects, so this is where we need to strengthen our efforts.
The Economics of the Transfer
Preliminary research has been done on the economic rationality of the East Route and the Middle Route. Both economize on investment compared to further development of local runoff and diverting the water of neighbouring basins. It is estimated that the project required to obtain 100 x 106 m³ of water by building new reservoirs in the mountain valleys of the Hai-Luan basin to store local runoff is about three times that of transferring water along the East Route. Each 100 x 106 m³ of water transferred from the Luan He to Tianjin would cost over twice as much as East Route transfer in terms of project investment. Compared with other water diversion projects, both domestic and foreign, south-to-north transfer project investment is not high either in terms of unit volume of water diverted or in terms of unit area irrigated. Although the total investment of the proposed project is relatively high, it is amenable to being done one section at a time beginning with the diversion canal head. Consequently, we can consider tentatively that this kind of project has numerous favourable elements economically. The problem is that some work remains to be done to make the economic justification more precise.
The project to transfer water from the Chang Jiang is multipurpose, supplying water not only to agriculture and aquatic products but also to industry, cities, navigation and the like. The comprehensive results produced by water supply differ from sector to sector. In some the relationship is direct between water supply and increases in output while in others it is not strong. The water transferred northward is to supplement the local water sources. In agriculture, the benefits of transferred water would be minimal in years of favourable weather but in years of great drought major reductions in output could be avoided as well as the economic and social problems engendered thereby. If areas which regularly suffer from the threat of drought could be provided with a reliable supply of water, they would be able to change their conditions of production and adopt various measures to produce high and stable yields, fundamentally transforming thereby the original backwardness. In addition, a change in the conditions of water control and communications can have a tremendous impact on the long-term economic development and social stability of an area which cannot be considered in a study of economic effects. For example, the irrigation projects constructed over 2,000 years ago in the Guanzhong plain of Shaanxi and the Chengdu plain of Sichuan, the Bian Canal excavated in the Sui Dynasty and the Beijing-Hangzhou Grand Canal built step-by-step since the Yuan Dynasty have all had an enormous impact on economic and cultural development for several hundred years or even longer after construction. A comprehensive analysis should be done of the effects of the proposed northward water transfer project on various sectors or regions. In addition, further studies are needed of project investment cost sharing, the scale and scheduling of the project and the degree to which the requirements of different sectors and different areas should be satisfied. The first step in this work is to assemble a reliable data base and to study definite applied computational methods.
The above takes as given the necessity of the proposed project. If we are to make a general proof of its economic feasibility we must also consider another aspect, that is, whether it would be rational economically to use other measures to attain the same goal. This requires first of all a consideration of the practicality of these other measures. We should also note that the principal water requirement for agricultural development on the plains of the middle and lower reaches of the Chang Jiang is to solve the problem of drainage, so that the transfer of a limited amount of water from the Chang Jiang would not hinder agricultural development there. Other feasible measures should be subject to economic comparison. These include the construction of more surface and groundwater storage projects to utilize local excess surface water; the development of sprinkler irrigation or changing over to drought-resistant crops in order to reduce water use; adopting multiple-use recycling technology to reduce industrial water use; and utilizing or desalinating sea water.
As with other water control projects, one of the most important aims of the northward transfer of water would be to improve the environment. Even though most of the environment would be improved, however, some parts could be affected adversely. Suitable measures must be taken to avoid those unfavourable impacts which can be avoided and reduce as much as possible those which cannot be avoided. Because the proposed transfer would affect quite a broad area, the problem of environmental effects must be treated prudently.
The problem of greatest concern is whether or not developing irrigation over large areas of the North China plain will lead to soil salinization. If this were to happen, it would mean that the proposed transfer project would basically be a failure. For the past two decades and more, we have not only obtained welldeveloped results in scientific research on the prevention of soil salinization in North China, but have also accumulated a wealth of experiences, both positive and negative, in engineering practice. Salinization has spread in some areas where this experience has been neglected and science has not been respected, but a number of irrigation districts have prevented salinization and obtained high and stable farm yields despite large-area irrigation. Therefore what should be discussed and studied is not whether the south-to-north transfer would lead to soil salinization but what kind of measures is it necessary to adopt to prevent its occurrence. Principally, we should grasp the following:
(1) We must implement comprehensive control of drought,
flooding and salinization in our planning principles;
(2) We must effectively control the water table with our technical measures;
(3) In project construction we must include all of the conveyance systems down to the field;
(4) We must set up appropriate management institutions and strict management rules and regulations in order to realize the above measures.
Another major question is the effect on the environment of the exporting region. To different degrees, each route would have an impact-the East Route on the lower reaches of the Chang Jiang and the Middle Route on the lower reaches of the Han Jiang. This aspect has not been studied deeply enough, but the main problem is clear. If the volume of water transferred exceeds the environmental capabilities of the exporting region, we should reduce the amount transferred. If the total volume transferred does not exceed the permissible limit but some unfavourable impacts are produced in the exporting regions during certain times (such as the low-flow period or the period of heavy water use in the exporting region), then we may adopt necessary measures to eliminate or reduce these impacts, such as building more projects to regulate the volume of water or the water table. Of course, these measures must be technically and economically feasible. The first thing to make clear at the present moment is the nature and degree of the impacts. For example, if we divert water from the Chang Jiang, it will reduce the flow of freshwater into the ocean, but just how large an impact will there be on the coastal ecology from this small reduction? Further research is necessary to determine the specific amounts so that a concrete economic analysis may be made and remedial measures adopted.
Changes in the ecological environment along the transfer routes should be forecast from all sides. The key to whether or not the schistosomiasis which is in the south will spread to the north due to the proposed water transfer lies in whether the host snails (Oncomelania) will move to the north with the water and breed there. A joint scientific research team headed by the Jiangsu Provincial Institute for the Prevention of Schistosomiasis has studied this topic since 1978. Its conclusion is that it is possible for the snails to migrate and spread to a certain extent north of 33°15' N. but a new snail zone will not form there as it is not suited to their long-term survival.
The ecological environment of aquatic organisms in the lakes along the route will be changed by the transfer and storage of water, but to what extent? How great an impact will there be on aquatic organisms? Which impacts will be unfavourable and which favourable? All these questions should be studied. We must pay attention to the great changes that have taken place over the past thirty years in these lakes. Furthermore, at times the ecological environment of the aquatic organism has been subjected to fatal destruction because water sources were not guaranteed, a condition which would not recur after the realization of the transfer project. Nonetheless, the development of aquatic organisms in the posttransfer ecological environment is a topic which urgently needs study.
There are numerous other environmental problems, some of which we may not yet recognize, and some of which may only appear after the water is transferred. This is difficult to avoid altogether.
(1) The project to transfer water from the Chang Jiang could
provide a rich source of water to the north, but it would only be
a supplemental measure. In the Hai-Luan basin we should first of
all make thorough use of the local water resources. Although the
local surface and groundwater is already utilized to a relatively
high degree, some potential remains. To further utilize the
surface water we must take into account the hydrological
characteristics of the Hai He and Luan He as well as the
coexistence of various kinds of natural disasters within the
basin. Even greater consideration should be given to the
technical and economic conditions for project construction. In
estimating the groundwater resource and the amount which can be
utilized, we must pay attention to the interchange between
surface and groundwater as well as to the spatial and temporal
variations in groundwater. In sum, the estimation of water
resources must be founded on a reliable base and the tapping of
the potential of local water resources must definitely be done
according to rational economic principles.
(2) Any increase in the diversion of water from the Huang He onto the Hai He plain must be premised on satisfying the requirements of the river itself and guaranteeing the water use of irrigation districts which are now diverting the Huang He. A further necessary condition is the proper handling of the sediment problem. At present it would be relatively practical and feasible to use appropriate engineering to divert some of the excess, relatively sediment free water of the Huang He during the winter non-irrigating season to solve the present urgent needs of the most seriously water-deficient regions.
(3) Analysis of the economic rationality of the transfer project has hitherto been insufficient, and work must be increased in this area. We must consider both the direct and indirect benefits of the project. With its extraordinarily broad scope, this project requires consideration of the benefits it would provide in the form of the conditions for the development of the other departments of the national economy.
(4) The impact of the water transfer on the environment must be treated cautiously, considering both possible improvements as well as those aspects leading to deterioration. We must study measures to prevent the deterioration of the environment based on our understanding of the objective laws of nature. The adoption of an appropriate strategy for the numerous possible environmental effects requires not only posing their nature but also studying the degree of their impacts.
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