ABSTRACT
For some water quality studies, methods to describe the relationship between flows and geometric characteristics are all that are required. Hydrologic methods to estimate variations in flows within a stream are generally referred to as hydrologic-routing techniques. Empirical models are limited to cases where available inflow and outflow data are sufficient to estimate empirical coefficients. The unit hydrograph theory is an extension of the rational method, devised in concept by Thomas J. Mulvany from the general state of the art in Ireland in 1851. A unit hydrograph is a hydrograph with a unit volume of runoff resulting from a storm event of specified duration and areal pattern. The continuity equation is simply an expression of the conservation of water mass. One common application of the continuity equation is in estimating storage for a known inflow and outflow hydrograph. Application of the Muskingum method generally involves two steps: calibration and prediction.
