ABSTRACT
Fig. 14.1 Routing of instantaneous inflow through a series of linear storage reservoirs. (Reproduced from V. T. Chow (Ed.) ( 1964) Handbook of Applied Hydrology, by permission of McGraw Hill.)
14.1 The Nash Model
The derivation of a unit hydrograph for a river catchment described in the last chapter is dependent on the availability of some rainfall and runoff records. Very often, information on river flows is required for streams and rivers that are not gauged. For large projects where· feasibility studies may occupy a few years, special temporary gauging stations may be established to provide the necessary data. However, design flow estimates may be required in a shorter time and, since the unit hydrograph represents the response of a catchment to a defined rainfall, many attempts have been made to synthesize the unit hydrograph; these methods can be found readily in the literature (ranging from Snyder, 1938, to NERC, 1975).
