| Our country is with shortage of water resources and water quality serious pollution, theagricultural water needs is always a major water user for the national economy. Althrough atpresent the proportion of agricultural water needs is reduced gradually, the industrial anddomestic water uses are increasing with the developing trend. But the agricultural waterrequirements will be still accopied the dominant position for rather longer periods. Soensuring the water use security and food security will be major faced task in long time.Therefore, to realize the reasonable allocation of water resources, improve the agriculturalwater use efficiency and management level, coordinate the water use contradiction betweenagriculture and ecology, realize the sustainable application for the water resources in riverbasin are the urgent problems to be solve at present. This research taken the secitificcalculation for the crop water requirements and analysis of the water demand process as forthe kernel, supply software and method support for the agricultural water research as thepurpose, using the modern methods and measures, has studied the calculating modelcomponent for the crop water requirements. Through combining the theoretic research withthe practice application, has put forward the systematic ayalysis method for the water demandprocess in an irrigation district. Obtained the major results and conclusions are as follows:1. According to the research results for the crop water requirements in domectic andabroad, collected, analyzed and screened the calculating models for the crop waterrequirements by estimating the ET0and crop coefficient. Using the COM componenttechnology has developed the model component software for the calculation of the crop waterrequirements. Taking the Active X DLL for the object model and standard, has completed12object functions to realize, basiclly covered all current common use methods of indirectcalculating methods for the crop water requirements. The component software included thecalculating methods for the crop coefficient and FAO Penman-Monteith as7independentobject classes, Penman Class, Radiation class, Temperature as4mixed object classes, and1auxiliary object class. Among them, the Penman Class included5Penman series ET0canculating methods; the radiation class included Priestley-Taylor and so on7ET0canculating methods based on e radiation; the temperature class included6ET0canculatingmethods based on temperature as Hargeaves-Samani and so on.2. Analyzed and summarized the water demand process in irrigation district whichinvolved the key problems as drought frequency analysis, calculation of ET0, determination ofeffective rainfall and calculation of irrigation water requirements and so on, has put forward the methods for systematically analyzing the water demand process in irrigation district.Included using the hydrologic frequency method, analyzed the water demand frequencyanalysis method. And through the typical irrigation district to carry out the verification, therepresentative was better, can be more accurately reflected the analysis precision foragricultural drough frequency; pointed to the determination of the effective rainfall, putforward the concepts of soil effective rainfall and crop effective rainfall. In order to facilitateanalysis of crop water demand process, introduced the ideas of urplus and deficit watervolume in calculating period, and summarized the method estimating effective rainfall monthby month using the soil storage water volume and soil effective rainfall in crop initial growingperiod; analyzed the characteristics of irrigation water requirements for whole growing periodmethod and monthly growing period method.3. The ET0values in a typical irrigation district have been calculated by the FAO PPP-17modified Penman formula and FAO Penman-Monteith method, the results shown that thelatter exhibited partial big with the average deviation about16%. Consider when absence ofcrop coefficient results pointed to the FAO Penman-Monteith method, the ET0calculatedresults by the FAO PPP-17modified Penman formula had better be adopted when calculatingthe ETc.4. Taking the Baojixia Irrigation District as for a typical example, has analyzed the waterdemand process, and compared with the actual diversion process. The maximal reference cropwater requirements were basically total distributed in June to July in each level year. Amongthem in the wet year, drought year or special drought year, it appeared in July. While in themoderate year or extreme dry year, it occurred in June. The ET0values in June and July willbe accounted for whole year volue as15.1%and14.8%respectively. Moreover during thefour monthes as May to August, the whole ET0value will be accounted about55.7%for thewhole year volue. The irrigation water requirements calculated by the whole growth periodmethod will be average large than6%~9%compared with the monthly calculated method.Integrated these two method results, the average annual deficit water volue was about220million m3. The irrigation demand period was mainly concentrated in June to August andMarch to May. The irrigation water requirements in summer season will be accounted about47%, in spring irrigation season will be accounted about49%, the irrigation waterrequirements in winter irrigation season was need less water. While the actual divertedirrigation water in winter, spring and summer season were accounted for26%,35%,39%respectively. But for this difference was presented consistent trend. If the agricultural wateruse produced irreconcilable conflict with the ecological water use, the winter irrigation wateruse can be reduced in a general year. |
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