HGS RESEARCH HIGHLIGHT – Fully Coupled Surface–Subsurface Hydrological Modeling to Optimize Ancient Water Harvesting Techniques
AUTHORS: Wim M. Cornelis, Koen Verbist, Tesfay Araya, Emmanuel Opolot, Jasmien C.J. Wildemeersch, and Bashar Al-Barri
We’re so proud that an entire chapter in the recently published “Handbook of Water Harvesting and Conservation: Case Studies and Application Examples” is dedicated to the modeling of ancient water harvesting techniques using HydroGeoSphere. In this chapter HGS was used to evaluate and optimize rain harvesting techniques across four case studies. Two of these case studies were from Chile, while the other two were in Ethiopia and Niger. The Chilean case studies evaluated the effectiveness of infiltration trenches (zanjas) in reducing surface runoff losses, promote recovery of natural vegetation and reduce land degradation. “In Ethiopia, the model was used to evaluate and optimize conservation practices with broad and narrow permanent beds, which are modified versions of locally called terwah and derdero systems.” And in Niger HydroGeoSphere models were used to evaluate several water harvesting techniques “includ[ing] scarification, zaï pits, and microcatchments like semi-circular or half-moon bunds (demi lunes)”.
The study demonstrates clearly the benefits of integrated hydrologic modeling in the evaluation of various water harvesting and conservation techniques.
“With [HydroGeoSphere] being originally developed to simulate surface–subsurface water flow and solute transport at a larger watershed scale, this chapter describes the first attempts to apply it for evaluating and improving water harvesting techniques at the field and small watershed scale. Whereas water harvesting studies are often based on a trial and error approach or at best on an empirical approach, the approach presented here has many advantages and provides a better understanding of water flow processes at or near water harvesting techniques.”
This study was co-authored by researchers at UNESCO, Ghent University, University of Fort Hare and Makerere University. For more information please reach out to the main author Wim Cornelis (Professor in Agro-Environmental Soil Physics at Ghent University; wim.cornelis@ugent.be).
CLICK HERE TO READ THE ARTICLE.
ABStract:
Recent developments in soil hydrology allow the use of complex distributed mechanistic models to describe hydrological processes at the field and catchment scale. These advances make it now feasible to use complex models to evaluate and improve ancient and present-day techniques. This chapter describes a method to evaluate rainwater partitioning and compute water balance components as affected by water harvesting techniques, using a fully coupled surface—subsurface process-based hydrological model. The methodology is illustrated with cases from Latin America (Chile) and sub-Saharan Africa (Ethiopia and Niger). The Chilean case demonstrates how the model was used to simulate runoff and soil–water content near and below infiltration trenches and how it was used to evaluate such existing practices at field scale. It also illustrates that the model shows good performance when applied on the much larger scale of approximately 3 ha watersheds. The chapter demonstrates how the HydroGeoSphere code can be applied in a water harvesting context.