Micro-catchment water harvesting in semi-arid regions: Basic design considerations

Abstract

In many parts of southern Europe (e.g. in most Mediterranean islands), water is not adequate for intensive irrigation development. In some other cases, due to various technico-economic reasons, water cannot be transferred over long distances. As a result, large areas remain without irrigation water and therefore they are solely dependent on rainfall. Rainwater harvesting, defined as the collection and storage of surface runoff water produced by rainfall for irrigation use, encompasses various practices, some of them having been known for many thousands of years. The great number of papers published on rainwater harvesting over the last two decades shows a renewed interest in this old technique and also its great potential under the recent socio-technico-economic conditions of many developing areas of the world. Although increasing interest is currently focussed on rainwater harvesting methods for arid climates, very little attention has been paid to semi-arid climates such as the Mediterranean climate. It is the objective of this note to discuss some of the aspects of design parameters of rainwater harvesting systems. Particular attention is focusses on the aspects of such hydrological design parameters as the expected soil moisture in the root zone at the beginning of the dry season under natural and rainwater harvesting conditions. Comparisons between these cases show a substantial improvement of the soil moisture regime under the rainwater harvesting technique and result in useful conclusions directly related to the design of rainwater harvesting systems.