Data View, Branch: Demand
Sites, Category: Advanced, Tabs: Methods The method for determining demands can be selected here. Currently three options are available: (1) standard water use method (2) FAO crop requirements approach and the (3) direct method.
In the simplest case, the user determines an appropriate activity level (e.g. persons, households, hectares of land) for each disaggregated level and multiples these by the appropriate annual water use rate for each activity. Monthly variation is applied to this rate.
The FAO crop requirements approach is typically used to represent agricultural demand nodes. This approach assumes for each demand site a set of simplified hydrological and agro-hydrological processes such as precipitation, evapotranspiration, and crop growth emphasizing irrigated and rainfall agriculture. Obviously non-agricultural crops can be included as well. These processes are used to determine the irrigation requirements for each demand site. Some of the basic assumptions are:
water balance is calculated at a monthly base
no carrying over capacity between months of soil water
water shortage is divided equally over the irrigated land classes
crop factors specified by month
yield response factor constant for entire growing season
See FAO Irrigation and Drainage Paper 56 (1998) for more details. This method can also be used to directly determine runoff contributions to rivers and groundwater supplies.
Demands can be directly read into WEAP from a file or monthly water use rates can be inputted.
Entered on: Data View, Branch: Demand
Sites, Category: Advanced, Tabs: Methods