title: Spatial and temporal estimation of runoff in a semi-arid microwatershed of Southern India.
abstract: In a semi-arid microwatershed of Warangal district in Southern India, daily runoff was estimated spatially using Soil Conservation Service (SCS)-curve number (CN) method coupled with GIS. The groundwater status in this region is over-exploited, and precise estimation of runoff is very essential to plan interventions for this ungauged microwatershed. Rainfall is the most important factor governing runoff, and 75.8% of the daily rainfall and 92.1% of the rainy days which occurred were below 25 mm/day. The declines in rainfall and rainy days observed in recent years were 9.8 and 8.4%, respectively. The surface runoff estimated from crop land for a period of 57 years varied from 0 to 365 mm with a mean annual runoff of 103.7 mm or 14.1% of the mean annual rainfall. The mean annual runoff showed a significant reduction from 108.7 to 82.9 mm in recent years. The decadal variation of annual runoff from crop land over the years varied from 49.2 to 89.0% which showed the caution needed while planning watershed management works in this microwatershed. Among the four land use land cover conditions prevailing in the area, the higher runoff (20% of the mean annual rainfall) was observed from current fallow in clayey soil and lower runoff of 8.7% from crop land in loamy soil due to the increased canopy coverage. The drought years which occurred during recent years (1991-2007) in crop land have increased by 3.5%, normal years have increased by 15.6%, and the above normal years have decreased by 19.1%. This methodology can be adopted for estimating the runoff potential from similar ungauged watersheds with deficient data. It is concluded that in order to ensure long-term and sustainable groundwater utilization in the region, proper estimation of runoff and implementation of suitable water harvesting measures are the need of the hour.
authors.affiliation: ICAR-Central Research Institute for Dryland Agriculture, Hyderabad, 500 059, India, rrejani10@gmail.com.
authors.forename: R
authors.initials: R
authors.lastname: Rejani
authors.forename: K V
authors.initials: KV
authors.lastname: Rao
authors.forename: M
authors.initials: M
authors.lastname: Osman
authors.forename: G R
authors.initials: GR
authors.lastname: Chary
authors.lastname: Pushpanjali
authors.forename: K Sammi
authors.initials: KS
authors.lastname: Reddy
authors.forename: Ch Srinivasa
authors.initials: ChS
authors.lastname: Rao
mesh_terms: D003247:Conservation of Natural Resources / Q000379:methods* / Q000706:statistics & numerical data; D055864:Droughts / Q000266:history / Q000706:statistics & numerical data; D040362:Geographic Information Systems; D049673:History, 20th Century; D049674:History, 21st Century; D007194:India; D011891:Rain; D045483:Rivers; D012987:Soil / Q000737:chemistry; D014872:Water Movements
chemical_list: D012987:Soil