| Fen River irrigation district is the largest irrigation district in Shanxi Province, its engineering construction and management level is more representative and leading in the province and even the country. Influenced by the special hydrogeological conditions of irrigation area, quota irrigation methods are used in most of the irrigation area, that is, spring irrigation at once a year, irrigation quota in240m3/mu, according to the traditional concept, the ratio of irrigation water is very low. But in fact, in terms of the special hydrogeological conditions (the depth of groundwater is approximately2.0m before irrigation), the groundwater recharged by the deep seepage of irrigation water, which leads to the rise of groundwater (the depth of groundwater increases to0.5-1.0m after irrigation). In the subsequent consumption process of soil moisture, the groundwater is continuously transformed into soil water, absorbed and used. The effective utilization rate is higher than the assessment value of traditional concept. Through the annual tracking and monitoring of the irrigation process, soil water supplement and consumption process and the change of groundwater level process, this paper reveals the quantitative relationship between the soil water movement characteristics of hydrological geological conditions and soil water and groundwater and the effective utilization coefficient of irrigation and so on, providing the basis for effective calculation and evaluation of high quota irrigation in the wells connecting with canals irrigation area under the special hydrogeological conditions and the technical support for sustainable development of Fen River irrigation managemnt bureau in Shanxi province.Mengfeng country irrigation area in Qingxu county was selected as a test area in this paper, according to the test requirements, local topography and hydrological conditions, three tracking test points were laid. The main test was field test and laboratory test was as a supplement. The field tracing test included groundwater, soil temperature, soil moisture, rainfall, layered irrigation amount of annual tracking and monitoring. The indoor test mainly included the determination of soil physicochemical properties, including the basic physical properties, soil nutrients and pollutants and so on.Based on the irrigation district field annual tracing monitoring data and field water balance equation, through the analysis of the change of each period stratified soil moisture, the groundwater level, rainfall and irrigation, this paper quantified the process of soil water conversion, supply and consumption under the means of quota irrigation and the availability of irrigation water. The results show that:(1)After the quota irrigation process of irrigation area was completed, the soil moisture content under the ground and above the groundwater level was supplied largely. At the same time, groundwater was of a significant increase. The irrigation water infiltration was the formation of groundwater recharge.(2)In the shallow groundwater in the area, the root activity between soil moisture content and groundwater were closely linked. The soil water content in the root layer gradually increased with the shallower of groundwater depth and the activity soil containing a quantitative relationship between the water content at depth of0-100cm(mm) and the depth of groundwater(cm): W=-0.0002z2-0.0391z+40.323, R=0.897。(3)The effectiveness of quota irrigation in irrigation area was the point in this paper. Through the calculation of the irrigation water using coefficient, this paper provided a strong basis for it. When calculating, the effective use was divided into two cases to calculate. The first one was only considering the water requirement of corn growth period, calculating the irrigation water using coefficient was64.1%; The second one was comprehensively considering the water consumption during the corn growth period and the soil water content of groundwater level during the period of after irrigation and before sowing, calculating the irrigation water efficient utilization coefficient was82.17%. From this, it can be known that the irrigation water efficient utilization coefficient in the irrigation area was in a high range, which fully demonstrated the effectiveness of the high quota irrigation in the wells combined with canals under the special hydrogeological conditions.(4)The content of heavy metals (copper, zinc, cadmium, chromium, lead and nickel) in the soil of Fen River irrigation area were measured by atomic absorption spectrophotometer (AAS) and the distribution characteristics of nutrients in the soil were analyzed. The results showed that the farmland of Fen River irrigation area was polluted by cadmium at different degrees owing to the long-term sewage irrigation and cadmium pollution was the main factor of soil risk; The content of six kinds of measured heavy metals were high in surface soil and the general vertical distribution of six kinds of heavy metals in the soil decreased with the increase of soil depth;(5)The nutrients of each sampling point were high in the surface soil of irrigation area; The distribution of nutrients had a certain regularity in the profile soil, the content of ammonium nitrogen didn’t have obvious changes with the increase of soil depth, the content of organic matter and nitrate nitrogen changed as "S", total phosphorus and total potassium had little floating in the middle part of the profile soil and showed a decreased trend in total.Through the study and analysis of the effectiveness of the high quota irrigation in Fen River irrigation district in Shanxi province under the special hydrogeological conditions, the validity of soil water movement and the distribution characteristics of heavy metals and nutrients in soil, this paper had important theoretical significance and practical value to increase the irrigation efficiency of Fen River irrigation district and the sustainable development of agriculture. |
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