A lack of technical knowledge has been identified as one of the primary factors preventing widespread adoption of rainwater harvesting amongst resource-poor farmers in semi-arid Tanzania. Experiments can fill this gap and help in the assessment and design of improved cropping systems, but the transfer of the results in time and space is difficult. A process-based, distributed agro-hydrological cropping systems model (Parched-Thirst) has been developed to enable the transfer of experimental results. It incorporates data pre-processors (climate generator, rainfall disaggregator and pedotransfer functions), soil moisture models, a rainfall-runoff model (including simple unit hydrograph runoff routing), the crop models Parch and Oryza_W, and analysis tools. The development process has been iterative, resulting in a model which is both very user-friendly and closely targeted to the needs of users. Results of a sensitivity analysis of the model suggest that predicted runoff is very sensitive to saturated hydraulic conductivity which is difficult to measure. Validation of model components and the model as a whole has been undertaken by third parties where possible as this lends the results greater credibility. Results suggest that the model is capable of reproducing observed data well over the range of conditions tested.
Young, M.D.B., Gowing, J.W., Wyseure, G.C.L. and Hatibu, N. 2002. PARCHED-THIRST - Development and validation of a process-based model of rainwater harvesting. Agricultural Water Management, 55: 121-140.