Study On Northern Large Irrigation District Canal-Well Combined Configuration Mode

Northern Large canal-well combined irrigation districts have an important role in ensuring food security, promoting coordinated development of regional economy and ecological environment. In recent years by the impact of climate change and human activities, northern irrigation district water resource became short, the contradiction between supply and demand of prominent, ratio of well and canal water imbalance, resulting in disorderly exploitation of groundwater, farmland ecological environment deterioration, serious impact on irrigation district of sustainable development, Therefore, it is of great significance to study the water configuration and the engineering configuration of canal-well combined in the large northern irrigation district.In this paper, selected Jinghui canal irrigation district in shann xi province as the research object, Based on the analysis of the characteristics of the water cycling of the canal-well combined irrigation district,Using the groundwater balance model, analyzed the conversion relationship between the elements of the cycle quantitatively; Based on minimum water deficit,contextual model that suite for the development of irrigation district has been studied out, the reasonable canal-well water ratio based on the minimum amplitude of groundwater level is determined; based on groundwater rational exploitation scale, reasonable layout of motor-pumped well and canal system of canal-well combined have been studied; management strategy of water resources sustainable utilization in the canal-well combined irrigation district t is discussed. The conclusion is mainly:(1) Generalized the irrigation water cycle system, through the analysis of precipitation, surface water(canal water) and groundwater(well water) transformation relation, It is considered that the canal-well combined irrigation changeed the path, intensity and structure of natural water cycle,come to the conclusion that available water resources in irrigation district are precipitation, surface water that from canal and groundwater that from well, the water was transformed under the influence of natural factor and irrigation and exploitation, transformation result is most directly reflect the underground water level dynamic.(2) Through the groundwater balance of irrigation district analysis showed that: recipitation infiltration recharge, canal seepage and field irrigation infiltration, well irrigation regression supplies is the major recharge source of groundwater in the irrigation district, more than 90 percent of the total recharge; exploitation is the main way of discharge of groundwater, more than 86 percent of total discharge in the irrigation district. Using GIS technology and mining coefficient method analyzed and calculated The groundwater exploitation potential of irrigation district, results showed that the area of groundwater overdraft account for more than 80 percent of the total area of irrigation district.(3)Based on the analysis of supply and demand balance of irrigation district, the balance of groundwater in four scenarios of the planning year(2020) is calculated, set underground water level amplitude of variation minimum as the criterion, determined the canal-well irrigation water ratio that fit for irrigation district, under 75 percent guaranteed rate and 50 percent guaranteed rate, the canal-well irrigation water ratio is 2.12,2.11.Under 50 percent guaranteed rate, each of spring, summer, winter season canal-well irrigation water ratio is 2.83,2.03,1.63; Under 75 percent guaranteed rate, each of spring, summer, winter season canal-well irrigation water ratio is 2.41,1.72,1.62.(4) Taking the minimum groundwater overdraft and the water shortage amount of the irrigation district as the target, the different groundwater exploitation scale scheme is proposed. According to the analysis and comparison of the results of groundwater balance calculation, the reasonable groundwater exploitation scale is 162.58 million cubic meters. Using single well control area method to calculate the hydrogeological partition of the reasonable number of wells and well distance, preliminary adjustment program is put forward to cut 10.9% of the irrigated district on the basis of the existing 16479 wells.According to the operation status of canal-well combined engineering, crop planting structure and characteristic of water requirement, low pressure pipeline, u-shaped channel of canal-well combined forms are studied, and preliminary planed the water transmission and distribution works and pipe network layout.(5)Problems of canal-well combined irrigation district management are analyzed, the management strategy of cana-welll combined irrigation district water resources efficiently and safely utilization is put forward from sound irrigation area of integrated water resources management system, promote the irrigation water price reform, strengthen supervision of irrigation district groundwater, improve irrigation canals and wells combined with engineering configuration construction aspect.