55- Catchment area (runoff area) is the part of the land that contributes some or its
entire share of rainwater to a target area outside its boundaries. The catchment
area can be as small as a few square meters or as large as several square kilometers.
It can be agricultural, rocky or marginal land, or even a rooftop or paved road. A
runoff area (catchment) with a sufficiently high runoff coefficient (impermeabil-
ity) would be optimal. - Storage facility is the place where runoff water is held from the time it is col-
lected until it is used. Storage can be in surface reservoirs, subsurface reservoirs
such as cisterns, the soil profile as soil moisture and in groundwater aquifers. - Target area (run-on) is the area where the harvested water is used. In agricul-
tural production, the target is the plan for the animal, while in domestic use, it is
the human being or the enterprise and it needs. A run-on area, where accumu-
lated water is stored and/or used. In most cases, the runoff is used to irrigate
agricultural crops with the water then stored in the soil profile. A high storage
capacity of the soil (i.e. medium-textured soils) and sufficient soil depth (>1 m)
are prerequisites here. The water retention capacity has to be high enough to sup-
ply the crops with water until the next rainfall event.
The most important parameters to take into consideration in practicing WH
include (i) rainfall distribution, (ii) rainfall intensity, (iii) runoff characteristics of
the catchment, (iv) water storage capacity of soils, (v) cisterns or reservoirs, (vi)
agricultural crops, (vii) available technologies and (viii) socioeconomic conditions
(Tauer and Humborg 1992 ; Mekdaschi and Liniger 2013 ).
CatchmentRunoffStorageTargetFig. 1 The main
components of a water
harvesting system
Water Harvesting in Dry Environments