My opinion on rational allocation of groundwater resources
(A) configuration objectives
Under the background that Changma Reservoir has been completed, the surface water can be coordinated by three reservoirs, and the reclamation scale of each irrigation area is basically determined, the adjustment of planting structure and irrigation layout is the main means, and the goal is to maintain and restore the ecological environment of the basin. Through analysis, the utilization direction of agricultural water resources in the middle and lower reaches of Shule River should be:
1) Maximize the development and utilization of groundwater in suitable mining areas in the middle reaches, save the transportation of surface water to the downstream, and solve the contradiction of competing for surface water with the downstream.
2) State-owned farms in old irrigation areas mainly develop well irrigation, supplemented by canal irrigation. Villages and towns generally maintain the status quo, but areas with conditions to develop well irrigation are gradually developing in the direction of well irrigation.
3) Well irrigation and well drainage are combined to achieve the dual purposes of ensuring irrigation and improving soil.
4) Existing water conservancy facilities should still be fully utilized, and adjustments can be made to exploit groundwater when necessary. Channels that need to be used for a long time should be lined with high standards and maintained in time to improve the utilization rate of water. In the well irrigation area, gradually improve the well irrigation facilities.
5) When selecting well irrigation area, the influence on spring water should be reduced as much as possible to ensure that Shuangta Reservoir can retain more spring water.
6) Through the joint operation of reservoirs, water resources can not only meet the irrigation demand, but also reserve some ecological water in natural rivers for downstream transportation.
(2) Basic conditions
1) The planning period is 10 ~ 30 years after the completion of Shule River Project.
2) Allocate according to the indicators of Shule River Project.
3) Prevent the salinization of new cultivated land in the project area.
4) The specific configuration adopts the third scheme of water resources utilization.
5) Distribution is based on the allowable groundwater exploitation in each irrigation area.
(3) Configuration opinions
According to the pumping data of Tuhulu No.23 hole in the hydrogeological investigation report of the middle reaches of Shule River, when the water level drops by 5.94m, the water yield is 80m3/h, the influence radius is 580m, the effective influence radius is 120m, the well spacing of interference wells is between 300 and 500 m, and the secondary salinization can be avoided by reducing the depth by 5 m.. Therefore, in Changma Irrigation District and Changma Irrigation District,
In the Shule River resettlement development project, the newly reclaimed land needs soil improvement: Dushanzi Branch Agricultural Development Zone in Huahai Irrigation District, with a land area of 1.45 million mu and a buried depth of less than 3m; The buried depth of the middle water level in the land of Huanghua Farm Development Zone in Changma Irrigation District is less than 3m, with a land area of 2 1.80 mu, a land area of 6,400 mu and a buried depth of 3-5m. Zhahua-Wangjiacaozi Land Development Zone has a land area of 410.3million mu with a water level lower than 3 m, 45,700 mu with a water level lower than 3 m south of the Twin Towers, and 25,000 mu with a water level of 3-5 m; The land area of Xiangyang Village Immigrant Development Zone in Shuangta Irrigation Area is 26,600 mu with water level below 5m, and the land area with water level below 3m is 3,800 mu. The land area of Yanzi Lake tributary whose water level is less than 5m is 97,300 mu.
Agricultural water-saving measures such as drip irrigation, sprinkler irrigation and changing crop planting structure were adopted in Danghe irrigation area to reduce irrigation quota and the number of agricultural mining wells. Irrigation quota is reduced from the current 660m3/ mu to 560m3/ mu, which can save 37.24 million m3/a of groundwater. By optimizing the original agricultural exploitation wells and shutting down some unreasonable exploitation wells, 850 agricultural exploitation wells can be reduced.
1. Changma Irrigation District, Ziqiao Irrigation District and Yulin Irrigation District
This area is the area with the richest groundwater and the best water quality in Shule River Basin. Except for the poor water quality (TDS greater than 3g/L) in the northwest of Ma Quan and the Qingshan Basin in the east, other areas are completely suitable for agricultural irrigation. At the same time, the aquifer here is shallow (mostly in 5 ~ 10m) and has good water abundance. Centrifugal pump is used for mining, and the water inflow of single well is above 20L/s in most areas, so the mining conditions are very favorable. In addition, the drainage condition of the shaft is very good, and it is easy to achieve the purpose of reducing the groundwater level and improving the soil. In addition, in terms of economic investment, the development of well irrigation has been proved to save manpower, material resources and financial resources more than the development of canal irrigation. More importantly, it can make full use of water resources and irrigate more land. With the rapid development of economy, the conditions for developing well irrigation will be more perfect, and some technical problems in well irrigation and drainage will not be difficult to solve.
The original cultivated land in Changma Irrigation District is 520,654,38+0,000 mu, and the cultivated land in Shule River Project is 65,438+0,654,380+0.92 million mu, which are mainly distributed in the peripheral wasteland and interlayer wasteland of Tuhulu-Qidaogou-Huangzhawan and other old irrigation areas. The irrigated area reached 639,300 mu. The current water use system in irrigation area is mainly canal irrigation, supplemented by well irrigation. There are 792 motor wells in the irrigation area with an output of 49 million m3. The calculated mining potential is 55 million cubic meters. Considering the guarantee rate, the exploitation potential is 50 million m3, and the irrigation area can make full use of groundwater resources10 million m3. According to the water consumption of 400m3/ mu, the groundwater of 654.38+000 m3 can satisfy the irrigation of 200,000 mu (the utilization rate of canal system is 80%). Therefore, in the extensive well irrigation areas, we should make full use of the existing canal system, determine a reasonable mining plan, adjust the mining layout, build border crossings, make full use of collecting wells, etc., and realize 200,000 mu of well irrigation or mixed irrigation areas. The remaining 440,000 mu is distributed in crops in deep water areas and non-well irrigation areas, and irrigation is undertaken by canal water. After the change of water use system, at least 0.55/0.62=0.88 billion m3 of canal water can be diverted (the utilization rate of canal system is 62%), and water can be abandoned from Changmaba to Gobi or transferred from the west trunk line to Shuangta Reservoir to supplement the groundwater in the basin and the downstream ecological water.
Suggestions for fragmentation configuration are as follows:
1) Shuangta Town-Bulongji-Sandaogou-Huangzhawan: Well irrigation has been developed in this area 165600 mu. The wasteland here is flat and contiguous, with good soil quality and relatively easy soil improvement. At the same time, the groundwater is rich, the water quality is good and the mining conditions are superior. Centrifugal pump mining is adopted, and the water inflow of a single well is between 10 ~ 100 L/s, and the TDS of groundwater in most areas is less than1g/L. The thickness of aquifer is generally 40 ~ 60m, and it can reach 80m in some areas. The buried depth of aquifer roof in most areas is 5 ~ 10m. According to the present situation of water and soil utilization, the water-rich degree of rock strata, the need for drainage and the difficulty of soil improvement, this area can be further divided into sub-regions. Tuhulu-Qidaogou is the most favorable division for developing well irrigation, and the south is the best section. In these two areas, the single well water inflow of centrifugal pump exploitation is 50 ~ 100 L/s, the groundwater TDS is less than 0.5g/L, and the aquifer thickness is 60 ~ 80m. It is also beneficial for Qidaogou-Sandaogou to develop well irrigation in other subregions, but the situation is slightly different. At present, this area is an old agricultural area with mixed irrigation of spring water and river water. Well irrigation can be developed vigorously in the south, and gradually in the spring irrigation area in the north, and the spring irrigation area will also develop in the direction of well irrigation. The spring water in Sandaogou-Taerwan sub-district is concentrated, and the development of well irrigation has a great influence on the spring water. At the same time, due to the shallow groundwater in this area, the well point drainage task is very big. Therefore, we can consider developing well irrigation in the near future and try not to reduce spring water.
2) Ma Yin-Huanghua area is planned to be an irrigation area combining well irrigation and canal irrigation, including 6,543.8+76 million mu of well irrigation and 654.38+6,543.8+67 million mu of canal irrigation. The low water abundance of rock strata in this area can not meet all the requirements of well irrigation development. At the same time, the canal system is relatively perfect, so it is appropriate to develop the combination of well irrigation and canal irrigation.
3) Qidaogou-Yumen Town and Qingshan Farm are canal irrigation areas with a total area of 448,700 mu. After years of development, this area has built more canals and become more and more perfect. Although this sub-region is located in the front of Changma Gobi, the groundwater is very rich and it is very beneficial to develop well irrigation, but the objective situation of the present situation must be considered, so it is planned as canal irrigation area. The quality of groundwater in Qingshan district is poor (TDS is greater than 3g/L) and the amount of groundwater is small, which is not conducive to the development of well irrigation at present and in the long run. Well layout is needed in the eastern part of the basin where the groundwater depth is less than 5m.
4) Ziqiao Irrigation Area: Soil salinization is serious, and phreatic runoff conditions are poor. To develop 670 thousand mu of well irrigation, it is necessary to develop well irrigation and well drainage and exploit groundwater.
5) Yulin irrigation area: the water level is shallow, the water quality is average, the soil tends to be salinized and the confined water is rich. The irrigation area has developed 6.5438+0.02 million mu of 24,000 mu of cultivated land into well irrigation and well drainage. It is planned to maintain the existing scale and further adjust the production well structure.
In addition, the soil and water quality of Nanqu-Tuhulu near the northern foot and the western edge of Ganxia Mountain are not good, so it is suggested to be used as an animal husbandry development area.
2. Shuangta Irrigation District and Xihu Irrigation District
The original cultivated land in Shuangta Irrigation District is172,400 mu, and the newly-added cultivated land in Shule River Project is106,900 mu, which is mainly distributed in the branches of the two lakes to the east of Anxi County and the edges of the old irrigation districts such as Huancheng, Nancha and Guazhou. The irrigated area reached 279,300 mu. The current water use system in irrigation area is mainly canal irrigation, supplemented by well irrigation. There are 634 motor wells in the irrigation area, with an output of 34 million cubic meters. The calculated mining potential is 60 million m3, and considering the guarantee rate, the mining potential is 48 million m3(80%), so the irrigation area can make full use of groundwater resources of 82 million m3. The net water consumption of crops is calculated as 400m3/ mu, and 82 million m3 of groundwater can satisfy the irrigation of 6,543,800+0,640 mu (the utilization rate of canal system is 80%). Therefore, the Shuangta irrigation area can be transformed from canal irrigation to canal irrigation combined with well irrigation. Considering the mining conditions, it is determined that the well irrigation area is126,600 mu, and the rest152,700 mu irrigation is undertaken by canal water. After the change of water use system, at least 77 million m3 of canal water can be diverted (the utilization rate of canal system is 62%), and the remaining water can be discharged from Shuangta Reservoir to the natural channel of Shule River to supplement the ecological water along the river and downstream.
1) Xiaowan District: Groundwater is mainly replenished by canal system, field irrigation and leakage of Shuangta Reservoir. The groundwater recharge is small, and the development of well irrigation can not be guaranteed. Therefore, it is planned to be a mixed irrigation area, in which well irrigation is 6.5438+0 million mu and canal irrigation is 0.79 million mu. Well water and canal water can be mixed irrigation, without well drainage.
2) Two Lakes-Nancha-Baiqibao: The buried depth of water level is more than 5m, and diving is normal, so there is no need for salt prevention. Canal irrigation is adopted, with an irrigation area of 6.5438+0.307 million mu.
3) Irrigation area around Guazhou and Huancheng: The buried depth of water level is less than 3m, and the confined water is rich, so it needs well irrigation, with an area of103,000 mu. The drainage conditions are general, so pay attention to the combination of drainage and irrigation.
4) West Lake Irrigation Area: The surface water and shallow confined water around this area are of poor quality and are not suitable for irrigation. There is only deep brackish water with TDS less than 2g/L below 200m in Gobi-Nanliang area of Daliang, which is an ideal water source to solve the drinking water problem in West Lake irrigation area and Nanliang area. Because of abundant water, it is not suitable for large-scale mining, so surface water irrigation is used.
3. Huahai Irrigation District
The original cultivated land in Huahai Irrigation District is 58,900 mu, and 73,600 mu of cultivated land has been added after the implementation of Shule River Project, mainly distributed in Bijiatan in the northwest of Huahai Township and Dushanzi branch canal in the southeast. The irrigated area reached 6.5438+0.325 million mu. At present, the water use system in irrigation area is mainly canal irrigation near Huahai Township and pure well irrigation area around Sanjiu Company. There are 206 motor wells in Huahai Irrigation District, with the exploitation amount of 0./kloc-0.1100 million m3, and the calculated exploitation potential is 200 million m3. Considering the guarantee rate, the exploitation potential is 0.10.60 billion m3(80%), and the irrigation area can make full use of groundwater resources of 270 million m3. The net water consumption of crops is calculated as 400m3/ mu, of which 27 million m3 of groundwater can meet 54,000 mu of irrigation (the utilization rate of canal system is 80%), and the remaining 78,500 mu of irrigation is borne by canal water. After the Shule River Project was implemented, Changma Reservoir transferred 70 million m3 of water to Chijinxia Reservoir. After the change of water use system, at least 26 million m3 of canal water can be diverted (the utilization rate of canal system is 62%), and the remaining water can be discharged from Jinchi Reservoir into Ganhaizi Lake area to supplement the ecological water along the river and downstream.
Farm of Huahai Basin Sanjiu Company 1): This area is a pure well irrigation area, and groundwater exploitation has formed a regional descending funnel, so the reclamation area is no longer expanded, and the current exploitation amount is maintained at 6.96 million m3/a. ..
2) Huahai Irrigation Area-Dushanzi Farm: The groundwater depth is 3 ~ 5m. If only surface water is used for centralized irrigation, the local groundwater level will rise seasonally, especially in the irrigation area north of Huahai Township. Therefore, canal irrigation should be used in the south of the irrigation area, and well irrigation should be used in the north, and the scale of well irrigation should be gradually expanded, reaching 39,700 mu of well irrigation and 56,300 mu of canal irrigation.
3) Pen rack beach: The water level is about 5m deep. At present, only surface water diversion and irrigation projects are built, and the utilization of groundwater is limited to people and animals. At present, the groundwater level has been rising. If the surface water is irrigated for a long time, the drainage system is not perfect, which is easy to cause salinization. Therefore, the mode of water use in irrigation area should be gradually changed, with canal irrigation as the main mode in the early stage and well irrigation and well drainage as the main mode in the later stage, and finally it will reach 6.5438+0.2 million mu of well irrigation and 22,000 mu of canal irrigation.
See Table 10-36 and Table 10-37 for the water resources allocation and groundwater development and utilization schemes of irrigation areas involved in Shule River Project.
Table 10-36 Water Resources Utilization Scheme of Shule River Project Area
Table 10-37 Plan of Groundwater Exploitation Well Location in Shulehe Project Development Zone
sequential
4. Danghe Irrigation District
Irrigation area is 327,400 mu, surface water is 290 million m3, and groundwater is 67 million m3. Well-canal water mixed irrigation method is adopted. At present, the groundwater exploitation exceeds the allowable exploitation (the allowable exploitation in Danghe River Basin is 46 million m3). Therefore, it is not appropriate to increase the planting area in Danghe irrigation area, and it is not appropriate to blindly increase the exploitation amount except for the urban water supply source area. New mining wells mainly replace abandoned mechanical wells in appropriate mining areas.
In the future, the direction of water resources utilization in irrigation area is: under the premise that the total amount of water resources will not increase, adjusting planting structure, preparing land on flat land, developing small border irrigation, spraying, dripping and pipe irrigation and other water-saving agriculture, reducing irrigation quota, making full use of groundwater resources, saving surface water resources, and discharging along Danghe River bed to alleviate the adverse environmental conditions along the crescent spring and the river. According to the calculation, the utilization potential of water resources in irrigation area is 40 million m3, and Danghe Reservoir can save 20 million m3 of surface water and discharge it into river bed.
The utilization direction of groundwater resources is: the recharge source of groundwater mainly comes from the leakage of Danghe River in different ways. Therefore, the groundwater in the irrigation area south of the diversion canal mouth is deeply buried, and river water irrigation should be the main method; To the north of Huang Qu-Huangdunzi Farm, the groundwater level is shallow (less than 3m), and well irrigation is the main method, supplemented by canal irrigation, and well layout is considered. Well irrigation should give priority to the exploitation of confined water with a depth of 50 ~100 m. On the one hand, developing well irrigation in the downstream can overcome the difficulty of insufficient irrigation in summer, on the other hand, it can reduce the rise of downstream water level caused by different types of surface water leakage in the upstream, strengthen the circulation of shallow confined water, and prevent groundwater from deteriorating due to long-term stagnation. At the same time, the well can also be used to irrigate salt, so as to gradually improve soil salinization.
Towns south of Dunhuang: including Qizhen and Yangjiaqiao. At present, the number of agricultural irrigation wells is 196 eyes, and the exploitation amount is 5.56 million m3. All agricultural irrigation wells in this area should be closed, and all irrigation tasks should be undertaken by surface water.
Dunhuang-Zhuanqukou: including Suzhou, Sanwei, Wu Dun, Mengjiaqiao, Lujiabao, Guojiabao and Dongfeng Farm. At present, the number of agricultural irrigation wells is 1 149 eyes, and the exploitation amount is 437 1000 m3. Some agricultural irrigation wells should be reduced in this area, and the exploitation amount should be controlled at 20 million m3. After adjustment, the well spacing is 450~500m, the well depth is a combination of shallow (80m), medium (80 ~ 120m) and deep (120 ~ 150m), and the water yield of a single well is 40 ~ 60m3/h. ..
Zhuanqukou-Huangdunzi Farm: including Zhuanqukou, Huang Qu and Huangdunzi Farm. At present, there are 473 agricultural irrigation wells, and the exploitation amount is19.83 million m3. This area can increase the production100000 m3. The planned well spacing is 750m, the well depth 120 ~ 150m, the production horizon is 40 ~ 150m, and the water output of a single well is 40m3/h. The well spacing in the drainage area is 300 ~ 400m.
See table 10-38 for the groundwater exploitation scheme of Danghe irrigation area.
Table 10-38 Utilization Scheme of Groundwater Resources in Danghe Irrigation Area
See figure 10-33 for the development and utilization scheme of groundwater resources in each irrigation area.
Figure 10-33 Opinions on Groundwater Development and Utilization in Shule River Basin
Second, the water source zoning of protected areas
The implementation of Shule River basin development project will greatly promote the development of local economy, thus promoting the development of local industry. As the economic and cultural center of the river basin, Yumen Town, Anxi, Huahai and Dunhuang will have a number of industrial projects to invest in, and the proportion of industrial water will increase. According to the available data, the reserve water sources designated in the above areas are as follows:
1) Yumen Town: At present, the groundwater is mainly domestic water and agricultural irrigation. Because the main aquifer in this area is Pliocene-Lower Pleistocene confined water, and the water head near Yumen Town is higher than the surface 1 ~ 6m, agricultural irrigation has little influence on the lower water quality, and it is located in the front of Gobi, with sufficient groundwater recharge, active runoff and excellent groundwater quality, which is not easy to be polluted. It is a good source of domestic water and industrial water. According to previous exploration, when the depth is less than 5m, the water inflow of a single well is greater than1000m3/d. At present, domestic water is supplied in a decentralized way. According to the needs of medium and long-term economic development, such as the construction of small and medium-sized water sources of 654.38+ 10,000 ~ 50,000 m3/d, the site can be selected locally. In order to improve the guarantee level, the site should be located in the southwest of Yumen Town as far as possible to protect the water source. If a large-scale water source with an area of more than 65438+100000 m3/d is built, it should be located in the alluvial fan area of Changma in the west of Yumen Town according to the water delivery requirements. The water source is the phreatic water in the gravel layer of Middle-Upper Pleistocene. Because of the abundant recharge source, high water source guarantee degree, no pollution source in the upstream of the water source and sufficient water quality guarantee, it can be used as the prospective water source of Yumen Town.
2) Anxi County: The present situation of urban water supply is decentralized water supply system. With the expansion of city scale, centralized water supply system is an inevitable development trend. According to the scale of a city with a population of 200,000, the domestic water and local industrial water will reach 50,000 m3/d. In order to reduce agricultural pollution, the northern Gobi and Shule River in Anxi County can be selected as water sources. Because of coarse sediment particles, rapid runoff alternation, good water quality and no agricultural irrigation, there is no need to set up water source protection scope. If a large-scale water source above 65438+100000 m3/d is built, another water source will be built in the ancient channel of Shule River in the south of the county, and the north and south water sources will operate at the same time to meet the water supply demand. The southern water source area is surrounded by agricultural irrigation areas, and the mining horizon should be the lower aquifer. Special investigation is needed to find a relatively stable cohesive soil layer as a water-resisting layer. The water source area should be protected, and the agricultural groundwater exploitation layer in the protected area should be strictly managed to avoid collusion between the upper and lower water layers and pollution of downstream water sources.
3) Huahai Township: At present, there is a centralized water supply system, and the water source is near Tiaohu. According to its development needs, the water source of 65438+100000 m3/d should be located at the edge of Gobi in the southwest of Tiaohu Lake in the upper reaches to prevent the groundwater in the water source from being polluted by agricultural irrigation.
4) Dunhuang City: It has been found that the most favorable groundwater exploitation area in Dunhuang City is located in the front of Danghe ancient river channel and Danghe alluvial fan near the city. The former is an ancient river phreatic water distribution area with a width of 2 ~ 3 km, aquifer thickness of > > 50m, water level buried depth of < < 30m, TDS < 1g/L, single well water inflow of > 1000m3/d ... The proven B-level reserve is 30,000m3/d, and the Danghe water source area has been built with a daily output of 654.33. The water source can expand the output to 7.5 million m3, which is the most promising area. The latter is rich in average water quantity and good in water quality, regardless of diving or confined water, TDS < 1g/L, single well water inflow > 1000m3/d, water level buried depth < < 20m, aquifer thickness > > 50m. Seven urban water sources have been built with an annual output of120,000 m3. At present, the proven reserves180,000 m3 have certain development and utilization prospects.
The above only discussed the location of water source qualitatively, and the specific implementation should be completed through special investigation according to the nature and quantity of water supply.