Arid and semi-arid areas are characterized by low annual precipitation rates which are
insufficient for plant growth, with precipitation depths in Western Desert in Iraq
ranging from 50 to 150 mm. The increasing pressures caused by climate change, water
shortages and poor quality have led to a scientific renaissance and innovative ideas for
water storage, including the development of water harvesting methods and systems,
which are the collection of rainwater from a surface and directing it in appropriate ways
to assemble it in a suitable place from which to be taken directly or collected and stored
for use at later times, for various purposes, the most important of which is irrigation,
domestic needs and feeding underground water basins.
Water harvesting systems contribute to improving the vegetation of degraded soils,
contributing to combating desertification, settling communities in those areas and
improving their living and environmental level. One fact to consider in the area of water
harvesting is that in marginal areas with rainfall rates of less than 250 mm per year,
production can only be continued and an acceptable level of productivity is guaranteed
under a irrigation system complementary to water needs so that this amount of water
is provided through water harvesting and a minimum rainfall of 100 mm in winter, or
150 mm in summer, has been adopted for water harvesting and supplementary
irrigation projects. According to certain considerations. The most important
component of the water harvesting system is the catchment area, storage facility and
cultivated area. . The most important factors to consider when harvesting water are the
distribution of rainfall, intensity of rainfall, properties of the runoff, water storage
capacity in the soil, reservoirs, agricultural crops, available techniques and socioeconomic
conditions. There are factors that mainly affect water storage quantities, the
most important of which are soil surface characteristics, soil type and precipitation
characteristics. The means of harvesting water are divided into two parts: microcatchment
systems, macro-catchment systems.