Modeling of flooding response and ecological engineering in an agricultural wetland region of central China.

摘要

Ecological engineering techniques are widely used in Chinese agriculture to reduce wastes and improve efficiency, but rarely to address crop loss associated with flooding. In the Jianghan-Dongting Plain of the middle Yangtze River basin in central China, large areas that were formerly shallow lakes and marshes are now empoldered for the cultivation of rice, fish and other crops. These areas are economically productive but regularly experience crop damage due to rainfall amounts exceeding the removal capacity of pumps and drainage canals.; A field investigation gathered existing data on landforms, hydrologic management, agricultural and aquacultural practices, production economics, and recent flooding events at two scales (Honghu Flood Diversion Area, 2800 km{dollar}sp2,{dollar} and Xiaogang farm, 24 km{dollar}sp2){dollar} within the lacustrine plain. A dynamic, pseudo-spatially distributed model was developed to simulate flooding and crop damage at these two scales. Simulated canal water elevations were calibrated at the farm scale for a 19-day flooding episode in 1996 and at the area scale for the 4-month rainy season over the years 1981-1994. Rice damage indices were derived as a function of time and area of inundation in excess of 1-day tolerance limits. Damage indices simulated at the farm scale for 1980-1994 were comparable in pattern to flooding-year yield reductions observed at the county level over the same period.; The model was used to simulate selected engineering strategies for reducing flooding loss. Increased pumping capacity at the farm level reduced internal flood levels and crop damage, but this benefit was reduced if the strategy was implemented areawide. Converting some low-position area to flood-tolerant crops such as lotus (Nelumbo nucifera) or wild rice stem (Zizanialatifolia) tended to increase internal flooding levels and damage to low position rice. These adverse effects were reduced or eliminated if dikes around flood-tolerant cropping areas were raised to provide passive water storage capacity, or if conversion were selectively implemented at the very lowest field elevations, or both. Economic evaluation of wide scale crop conversion is complicated by inelasticity of demand for lotus and wild rice stem in the absence of regional marketing or transportation structures.