The water balance equation for the non-irrigation area is similar to the one for the irrigation area, except for the items where humans are directly involved, Do and D, as follows:
Pni + Gni + X - Eni - S - Sni = 0
(6)
Pniprecipitation over non-irrigation area
Gnigroundwater recharge to non-irrigation area
Enievaporation from non-irrigation area
Sartesian outflow
Sniwater storage change in non-irrigation area
where, Gni is groundwater recharge to non-irrigation area, Eni is evaporation from non-irrigation area, S is artesian outflow, and
Sni is change in soil and ground water storage in non-irrigation area. Two land use types, native plants land and waste land in non-irrigation area, were specified in this study. Based on the formulation of Mao et al. (1999,1997) and Zhao et al. (2000), evaporation from non-irrigation area was estimated as:
Eni = minE0 . e(H-R), . (H - R)
(7)
E0water surface evaporation
Hwater table depth
Rmean root depth of vegetation
,,empirical soil parameters
where, E0 is water surface evaporation, H is water table depth, R is mean root depth of vegetation,
,, are empirical soil parameters. The artesian outflow inside the study area was computed from the investigation and was assumed to be constant.
