Study On The Process Of Irrigation And Drainage And Water Management Of Paddy Field In Plain River Network Area

The Polder area in the southern China is flat, the rainfall is abundant, the rainfall runoff storage capacity is weak, the utilization rate of rainwater resources is low, coupled with extensive farmland water management, the above reasons causes farmland irrigation water waste is serious and unilateral water food output is not high, especially in the process of water management in rice, farmland drainage in the process of pollutant emissions has not been effectively controlled, these has brought great pressure to the water environment ecological protection area. In order to study the drainage and irrigation of the Polder area in the southern China, in this paper, we present a systematic study in Changshu, Jiangsu Province. According to the field observation of groundwater level change, the field soil water content and underground pipe displacement data, we analyze the relationship between groundwater level and soil water content to conclude that the lower water level is the index of the paddy field. By using the DRAINMOD model to simulate the hydro logical cycle of paddy field drainage to obtain the appropriate layout scheme of the underground drainage system. Then we design and develop the high efficiency water management computer aided system. The main research results are as follows:(1) According to the relationship between soil water content and groundwater depth, we can calculate the groundwater depth index to determine the lower limit of irrigation in accordance with the percentage of saturated water content of the soil moisture content. When the test area groundwater buried depth is more than 30cm, up to 35cm, the volumetric soil moisture dropped to about 80% of saturated water content, close to or below field capacity, it will go ill with the rice’s growth. Therefore, the lower limit of irrigationit can be limited to 30-35cm under the ground.(2) Using DRAINMOD model we can calculate the continuous process of hydrological changes in farmland, by comparing with the actual measurement of groundwater depth and drainage in paddy field, we found that the daily variation of the groundwater depth and the corresponding displacement of the paddy field in the DRAINMOD model was consistent with the measured values. So the DRAINMOD model can be used to analyze the hydrological cycle process of farmland in Changshu test area as the representative of the southern plain river network area.(3) According to the variation of the leakage of rice during the growth period with the change of the distance of the underground pipe by using the DRAINMOD simulations, when the underground pipe is buried at 90cm deep, the amount of water can reach the appropriate 600mm leakage of rice growth, this value is much larger than that of the existing dark tube placement (8m) in the test area. Therefore, in determining the distance of drainage, it is required to accurately determine the parameters affecting the calculation of drainage spacing, in particular, the lateral drainage rate of farmland to ensure that the appropriate leakage displacement.(4) We set up a Computer aided system for water management, based on the water balance equation. By repeatedly calling the data, method and model of the system to simulate the production process of the farmland. Finally, the feasible irrigation management plan is recommended to the decision maker through the program evaluation.