ABSTRACT
In recent years, changes in catchments water balanc
e due to land use management have
become the main concern of water resources authorit
ies in Iran. Due to rapid population
growth and land use changes, especially constructio
n of Taleghan dam, Taleghan
catchment has undergone rapid changes such as urban
development, declining of
rangelands, and deterioration of environment and er
osion of soil resources by cultivating
the hilly lands along the slopes for wheat or barel
y production. The extent of rangeland
area shrinkage is substantial: from 83% during the
early stages of dam construction
down to 35% by the end of the study period. The ‘go
od’ rangeland area decreased to
5.90% from 34.49% while the poor rangeland increase
d from 19.04 to 23.35% during the
period of 1987 to 2007. These changes could potenti
ally have devastating impacts on
water balance of the catchment. The main objective
of this research was to examine the
effects of land use changes on water balance of the
Taleghan catchment before and after
the dam construction. The Soil and Water Assessment
Tools (SWAT) model was applied
for predicting water balance in the middle and outl
et of the catchment. The main input
data for simulation of SWAT are Digital Elevation M
odel (DEM), soil type, soil
properties, and hydro-climatological data. Comparin
g the water balance for 1987's land
use for the middle station (Joestan) and the outlet
station (Galinak) showed that surface
runoff was 21% of the precipitation for the upper p
art of the catchment and 33% at the
outlet. Total groundwater and lateral flows were 37
and 19%, respectively. The water
balance at the outlet was predicted for two other s
cenarios of 2001 and 2007. The results
showed 7.3% increase in surface runoff and 11.3 and
11% decrease in the lateral flow and
groundwater flow, respectively. These results indic
ated progressive increase in surface
runoff and decline in interflow and groundwater flo
w.Therefore, one of the main
challenges facing development planners is the contr
ol of the accelerated degradation of
the natural resources that has been taking place du
ring the last decade.