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Wageningen Universiteit (1994)

Rainwater harvesting in arid and semi-arid zones

Boers, T.M.

Titre : Rainwater harvesting in arid and semi-arid zones

Auteur : Boers, T.M. 

Université de soutenance : Wageningen Universiteit

Grade : PhD thesis 1994

In arid and semi-arid regions, the scarcity of water can be alleviated by rainwater harvesting, which is defined as a method of inducing, collecting, storing, and conserving local surface runoff for agriculture. Rainwater harvesting can be applied with different systems, and this dissertation deals with the system of micro-catchments. A microcatchment consists of a runoff area and a basin area in which a tree is planted. The purpose of this study was to develop a design procedure for micro-catchments, applicable to environmental and human conditions prevailing in developing countries. Underlying the design procedure is an analysis of the water balance of the system.
The design method is based on a prediction of actual transpiration by the numerical soil-water-balance model SWATRE, while the runoff component is predicted by a runoff model. The design- aims at sufficient soil water being available in an average rainfall year. Deep percolation losses occur in wet years, and water shortages in dry years. A tree suitable for these conditions is able to withstand dry periods and drought years. The practical problem selected for this study was the establishment of Neem windbreaks in Niger and Nigeria. Points to consider in the design are the seasonal distribution of rainfall, the soil hydraulic conditions, and the tree hydrological/ physiological characteristics.
The theory of four surface runoff models is presented. These models are compared in their capability and accuracy to predict runoff volumes for micro-catchment design and in their model concept, structure, parameters, and input data requirement. A kinematic-wave model with depression storage and a linear regression model are considered the most suitable for micro-catchment design. The theory of the soil-water-balance model is discussed, as is the calibration of this model with data from Sede Boqer in the Negev Desert. The application of the model for micro-catchment design is demonstrated for an extremely and zone and an and zone in the Negev Desert.
The extremely and zone is too dry for rainwater harvesting from micro-catchments, larger catchments being required there. In the and zone, the basin areas should be approximately 40 m 2for each tree, and the runoff areas 60 m 2. The design approach is applied to five weather stations in Niger and northern Nigeria where data were available. Data from a Neem windbreak at Sadoré in Niger were used to calibrate the model. Data from Niamey, near Sadoré, were used to compare runoff prediction with two runoff models and to predict micro-catchment design. The combination of a runoff-depth model and the soil-water-balance model was used to predict microcatchment design at Sadoré, and Tahoua in Niger and at Sokoto and Katsina in Nigeria.

Mots clés : water harvesting / runoff farming / models / research / unproductive land


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