Application of shallow water equations to analyze runoff processes in hilly farmlands     

Kei Ishida  Macarius Yangyuoru  Koichi Unami  Toshihiko Kawachi 《Paddy and Water Environment》2011,9(4):393-401

Analysis of runoff processes in farmlands during storm events in particular is an important engineering topic. The shallow water equations describing the physical conservation laws are attractive tools for understanding motion of surface water. A numerical model is developed to reproduce surface water flows during storm events, using the finite element method and the finite volume method applied to the one-dimensional shallow water equations. The numerical model has the advantage of dealing with transcritical flows, wet, and dry processes, irregular channel bed slopes, and channel junctions involving multiply connected networks. Standard numerical tests demonstrated some of these features. Runoff processes from farmlands in a Japanese hilly area is analyzed with the numerical model coupled with another runoff model of black-box type. Parameters of the models are calibrated and validated using observed series of rainfall and runoff discharge data. Simulated results included submergence of hydraulic jumps and flood storage in farming plots, which are very informative in terms of assessing diverse functions of the farmlands.  相似文献   

Weed management on Vertisols for small-scale farmers in Ghana     

E.O. Darkwa  B.K. Johnson  K. Nyalemegbe  M. Yangyuoru  C. Oti-Boateng  T.J. Willcocks 《国际虫害防治杂志》2013,59(4):299-303

Vertisols and vertic clays represent a vast crop production resource (300 million hectares world-wide) that is underutilized, mainly because of problems with soil physical characteristics (particularly relating to water) and weeds. These montmorillonitic clays are generally more fertile and have higher water-holding capacities than many tropical soils, but they are difficult to manage as they are very sticky when wet and hard and cloddy when dry. Research in Ghana has shown that it is technically possible to increase crop yields by 90% in normal wet seasons by using raised (camber) beds to control water, but further increases in yield potential are prevented by highpopulations of Cyperus rotundus L. and Imperata cylindrica (L.) Raeuschel. These challenges have been addressed by research on farms and on a research station to determine the effectiveness of glyphosate and camber beds for weed and water management and crop production in maize-based farming systems. Field trials have shown that tuber populations of C. rotundus could be reduced by 95% after glyphosate at 1.8 kg a.e. ha-1 was applied at the beginning of four cropping seasons during 1997 and 1998. The combination of glyphosate for weed control and camber beds to shed excess water produced maize grain yields of 3.5 t ha-1 - a significant increase over the typical yields of ～1.0 t ha-1 withtraditional methods ofhoe-weeding onflat land. Economic evaluations have shown that the returns to small-scale farmers could be considerably increased by the use of glyphosate for weed control.  相似文献