Institut für sozial-ökologische Forschung (ISOE)
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Rain- and floodwater harvesting (RFWH) technologies and water reuse are ideal and generalpurpose technologies to improve water security and to contribute to climate adaptation – in particular for semi-arid regions. These technologies are part of a multi-resources mix within an integrated water resources management (IWRM). They create capacities to buffer water fluctuations and alleviate water scarcity. In this way, they reduce the pressure on existing resources, and can stimulate local economies. However, in order to be sustainable, these technologies need to be adapted to the local context – through suitable design, adapted operation requirements, and a back-up by training users and operators accordingly.
The design of rainwater harvesting based gardens requires considering current climate but also climate change during the lifespan of the facility. The goal of this study is to present an approach for designing garden variants that can be safely supplied with harvested rainwater, taking into account climate change and adaptation measures. In addition, the study presents a methodology to quantify the effects of climate change on rainwater harvesting based gardening. Results of the study may not be accurate due to the assumptions made for climate projections and may need to be further refined. We used a tank flow model and an irrigation water model. Then we established three simple climate scenarios and analyzed the impact of climate change on harvested rain and horticulture production for a semi-arid region in northern Namibia. In the two climate scenarios with decreased precipitation and medium/high temperature increase; adaptation measures are required to avoid substantial decreases in horticulture production. The study found that the most promising adaptation measures to sustain yields and revenues are a more water efficient garden variant and an enlargement of the roof size. The proposed measures can partly or completely compensate the negative impacts of climate change.