Contents preface (VII) introduction 1—37

2.5.1. Runoff—Rainfall Relations
Yield of a river is the total quantity of water that flows in a stream during a given period. One can estimate the yield of a river by either correlating stream flow and rainfall or using some empirical equation or some kind of simulation.
By plotting measured stream flow i.e., Runoff R versus corresponding rainfall P and drawing a best-fit line (or curve), one can establish an approximate relationship between rainfall and runoff. Alternatively, one can establish rainfall-runoff relationship using regression analysis.
Some empirical relations have been developed using the observed rainfall and runoff for streams of a given region. Such relations, therefore, have limitations to their applicability only to specific regions.
Based on his studies of small catchments (less than about 150 km²) of U.P., Barlow expressed the runoff R as (8)

HYDROLOGY	59
R = Kb P	(2.13)

in which, K_b is the runoff coefficient, Table 2.1, that depends on the catchment and monsoon characteristics.