Discussion on Estimation Method of Water Storage Benefit of Terrace

Abstract

[Objective] On the basis of considering the differences of soil property, terrace form and rainfall type, we aimed to establish the estimation method and framework of water storage and retention efficiency of terrace. [Methods] By using soil reservoir calculation model and infiltration model, we explored the prediction methods of soil water distribution in saturation-excess runoff and infiltration-excess runoff. Moreover, based on the Richards equation, we analyzed the two-dimensional infiltration of soil profiles at different field and ridge boundaries. On this basis, we constructed the scenario of soil water movement under single runoff generation mode or two runoff generation modes under four types of rainfall patterns, including pre-peak rainfall, uniform rainfall, post-peak rainfall, and stepped rainfall patterns. [Results] We proposed the distributed estimation method of soil water storage efficiency of terrace field, and the maximum water storage capacity (WM) of soil in a single terraced field was calculated. For different types of terraces, the anti-lateral seepage effect of stone walled bench terrace was the best, and the anti-lateral seepage effect of earth banked terrace was the worst, and the new soil ridge terrace with large pores, small density and short construction time lost more water than the soil ridge terrace with long construction time. The critical time (t) of full flow production under different rain patterns was obtained. [Conclusion] This estimation method could greatly reduce the dependence on field facilities and equipment, and reduce the input cost. With the help of field investigation and sampling, the efficiency of terraced water storage could be estimated based on model simulation. In addition, the method could be used to estimate the water storage efficiency of terrace on a regional scale according to the distributed calculation data of the water storage efficiency of a single terrace field, and provided a reference for the estimation of the water storage efficiency of different regional terraces.

Keywords

• terrace
• rainfall type
• runoff generation
• efficiency of water storage
• infiltration