Water resources of Balochistan, an arid province of Pakistan, are extremely scarce and limited. It is highly imperative that these resources be used most judiciously to ensure sustainable agriculture development and productivity. This, in turn requires knowledge of crop water requirements (CWR) in various agro-climatic zones of the province. Lack of this information often results in farmers over or under irrigating their fields with consequent loss in yields and production. Various agencies in the country have determined CWR values for the Indus Basin; however, for Balochistan the water requirements of various popular crops have not been estimated.
In this study, historical meteorological data such as maximum-minimum temperature, relative humidity, wind speed, sunshine hours and rainfall were collected from 15 stations in Balochistan for the last 44 years (1961-2004). CropWat 4 Windows Version 4.2 was used to determine reference evapotranspiration (ETo) at different locations in the province. Isohyets, elevation, maximum, minimum temperatures, relative humidity, ETo and rainfall contour maps were developed. Based on these maps, the province has been divided into seven zones. Zone I includes Gwadar, Turbat, and Panjgur districts. Annual rainfall in this zone is very low and varies from 36-110 mm and increases with increase in altitude. Maximum rainfall occurs in the months from January to March (45 to 73%) and minimum during monsoon. Therefore, this zone is out of the monsoonal belt. The average ETo is very high along the seashore (>10 mm/day) due
to high wind speed and arid climate. The ETo decreases with increase in altitude. The main crops grown are dates, wheat, onion, and fodder.
Zone II consists of Chagi and Kharan districts with annual rainfall varying from 30-160 mm. Maximum rainfall occurs in the months from January to March (30 to 50%). This zone is also outside the monsoonal belt. The average ETo varies from 5.10 to 8.5 mm/day. The main crops grown are dates, wheat, and onion.
