کامران چپی

More than 50% of total water quality impairment originates from non-point sources., and runoff from agricultural land is one of the major contributor to non-point sources. Therefore, the identification and quantification of runoff generation areas is crucial for source water protection and nutrient management. This paper has two focuses: i) the identification of possible approaches available in the literature to identify runoff contributing area, and ii) the development of a field procedure for identification of runoff generating areas. A wireless runoff sensor network was used in a small agricultural watershed to monitor runoff generating areas from rainfall events during late spring, summer and early fall. The results show that runoff generating areas are highly dynamic varying from 0 to 100%. About 15% of the watershed generates 75% of surface runoff during summer, 100% in fall and 45% during late spring. The factors affecting variability of runoff generating areas varies with season; however, the soil moisture and rainfall intensity play the dominant role. The sensitivity of field(s) in a watershed to runoff generation remains constant, i.e. specific fields responded first during all seasons. The results also indicate an index based on Slope and Area has a potential for the identification of sensitive fields in a watershed.