Land Use

(These parameters apply to the Simplified Coefficient Method. For the Soil Moisture Method, see Soil Moisture, Land Use; for the MABIA Method, see MABIA, Land Use; for the Plant Growth Method, see Plant Growth Model Method, Land Use.)


The land area for a catchment or subcatchment, or the share of land area from the branch above.  Note: You can use WEAP's Automatic Catchment Delineation to help you calculate catchment area.


The crop coefficient, relative to the reference crop, is given here for each land class type.  There is a special case involving Kc and double cropping.  In cases where there are two different crops planted on the same land at different times of the year (double cropping), you can choose to model this with two separate branches on the demand tree, one for each crop.  In this case, set the Kc = 0 for branch 2 when branch 1 is active and Kc = 0 for branch 1 when branch 2 is active.  For example, if winter wheat was planted November through March and corn was planted May through September, the Kc's may look something like this:

Wheat: Kc = MonthlyValues( Jan, 1.15,  Feb, 1.15,  Mar, 0.4,  Apr, 0.05,  May, 0,  Jun, 0,  Jul, 0,  Aug, 0,  Sep, 0,  Oct, 0,  Nov, 0.4,  Dec, 0.7 )
Corn:    Kc = MonthlyValues( Jan, 0,  Feb, 0,  Mar, 0,  Apr, 0,  May, 1,  Jun, 1.15,  Jul, 1.15,  Aug, 1.05,  Sep, 1.05,  Oct, 0.05,  Nov, 0,  Dec, 0 )

Double cropping could also be modeled with one branch, where the various crop and land use parameters would change over the year to reflect the two different crops.  The important point to remember is that Kc should not be set to 0 unless you are double cropping.  When Kc = 0, WEAP will ignore that land entirely, including no precipitation, evaporation or runoff.  For fallow land, set Kc to a small but non-zero value, such as 0.05.

Effective Precipitation

The percentage of rainfall available for evapotranspiration. The remainder is available for runoff.


Average land slope in degrees (0 = completely level, 90 = completely vertical).  Filled in by automatic catchment delineation.  Not used in calculations, although could be used in an expression to help set Effective Precipitation.

See also: Simplified Coefficient Method Calculation Algorithm

Entered on: Data View, Branch: Catchments, Category: Land Use, Tab: Area, Kc, Effective Precipitation.