Determination of spatial water requirements at county and regional levels using crop models and GIS: An example for the State of Parana,Brazil

Due to the competitive use of available water resources, it has become important to define appropriate strategies for planning and management of irrigated farmland. To achieve effective planning, accurate information is needed for crop water use requirements, irrigation withdrawals, runoff and nitrate leaching as a function of crop, soil type and weather conditions at a regional level. Interfacing crop models with a geographic information system (GIS) extends the capabilities of the crop models to a regional level. The objective of this study was to determine the irrigation requirements, annual runoff and annual nitrate leaching for the most important crops of the Tibagi river basin in the State of Parana, Brazil. The computer tool selected for this study was the Decision Support System for Agrotechnology Transfer (DSSAT) version 3.5 (98.0) and its associated crop modeling and spatial application system AEGIS/WIN. It was assumed that farms within the same county use similar management practices. To achieve representative estimates of irrigation requirements, the weather data from stations located within each county or the nearest weather station were used. A weighting factor based on the proportion of soil type and crop acreage was applied to determine total annual irrigation withdrawals, annual runoff and nitrate leaching for each county in the river basin. The model predicted outputs, including yield, irrigation requirements, runoff and nitrate leached for different soil types in each county, were analyzed, using spatial analysis methods. This allowed for the display of thematic maps for irrigation requirements, annual runoff and nitrate leaching, and to relate this information with irrigation management and planning. The maximum annual irrigation withdrawal, runoff and nitrate leaching were 22,969 m³ per year, 31,152 m³ per year and 1488 t N per year in the Tibagi river basin. This study showed that crop simulation models linked to GIS can be an effective planning tool to help determine irrigation requirements for river basins and large watersheds.     

基于ET管理的土地整理水资源供需平衡分析——以河北省魏县车往镇基本农田土地整理项目为例

以土地整理中水资源供需平衡为基础,引入基于ET管理的水资源供耗分析,为缺水地区水资源供需平衡提供一种依据。以魏县基本农田土地整理项目为研究对象,建立基于ET理念的水资源平衡关系,分析项目区可利用水资源量及耗水量(即ET值),得出不同水平年下的供需结果。研究结果表明,现状水平年下水资源缺口29.81万m3,2010年项目区采取措施后综合ET值降低,盈余水量20.07万m3,实现了水资源供需平衡。