| On the basis of consulting to a number of literatures both at home and abroad, and understanding the present situation and trend of studies on water and salt dynamics, water and salt movement and the models concerned are reviewed as a whole. At present, it is relatively difficult to find the successful examples about the concept models used for simulating and computing the regional water and salt movement and its change laws. The following contents are researched using the existing water and salt balance model.1. Improvement of the regional water and salt balance modelWater and salt balance model used in this paper is developed in response to the Tarim Basin irrigation and environment protection project, which uses the World Bank loan. The model belongs to the conceptual model, and is a parameter distribution model, too. In the course of using, a number of problems within the model are found out and the simulation accuracy is not satisfactory. The errors are corrected, such as writing, formulas, variables and their values for calculating in the program. In terms of the real features of geology, climate and river hydrology, etc. of Hotan sub-project area, the computation ways of the river width and storage change are improved. The regional water and salt balance model after improvement can describe the present situation of Hotan sub-project area and the simulation accuracy is better than before.2. Calibration, verification, forecast and evaluation of the water and salt balance modelThe water and salt balance model is written in TORTRAN, a computer language, which consists of 1 main program, 11 sub-programs and I parameter file which declares and interprets the parameters used in the model. The water and salt balance model has the characteristics of explicit structure, definite concepts and convenient application. 33 data files in which the data are got from observation, investigation and estimation of the local technicians are prepared before running the model program. For the water and salt balance model, the data series from 1971 to 1990 are used for calibrating the parameters, and the XIAN UNIVERSITY OF TEChNOLOGY THESIS FOR ACADEMIC DEGREE ABSTRACTcorresponding flow series from the Xiaota hydrological station are viewed as the standard of the parameter calibration. A set of optimal parameters is obtained after adjusting the variable parameters and comparing the observed flow records and the calculation results from the model repeatedly. Then, model verification using the data from 1991 to 1995 is carried out, and model prediction using the data from 1996 to 1998 is conducted, too. It is showed by above work that this conceptual model has high accuracy and applicability. Therefore, it can be used for simulating water and salt dynamics and its future trend for Hotan sub-project area.3. The present situation of water and salt balance for Hotan sub-project areaAfter comprehensive parameter calibration of the water and salt balance model, the present situation of water and salt balance are simulated and calculated in Hotan sub-project area. The trend analysis of flotan river water shows that the annual surface runoff has the degressive trend, but not remarkable, ~vhich has the potential threat to the irrigation agriculture in 1 Iotan sub-project area. On the basis of analysis, affected by the surface runoff, water diversion for irrigation has the degressive trend, too. Water loss of seepage and surface evaporation of reservoirs is serious in Hotan sub-project area, and the effective utilization degree of reservoir storage water is too low to not be good at solving the problem of the spring water shortage for irrigation. Recharge of groundwater is very abundant to make the groundwater table less than I .Sm in most places within the sub-project area. The main sources are water loss of canals seepage, farm irrigation seepage, river seepage, etc. The potential evaporation is serious through the barren land. On the basis of water balance calculation of irrigation units, spring irrigation is limited... |
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