Use of Regional Hydrometeorological Relationships in Operational Hydrology

Abstract

Synthetic streamflow models are increasingly being used in the planning, design and operation of water resources systems. Unfortunately, the historical data required for their calibration is often inadequate or non-existent. The principal aim of this project is to show how, through the development of regional hydrometeorological relationships, the available data may be used to evaluate reliable model parameters for ungauged catchments. The study is based upon the region of England and Wales containing the Rivers Teifi, Tywi, Usk, Wye, Teme and Upper Severn. A computer method of identifying possible errors in monthly data sets is developed and used for the verification of data supplied by the Water Data Unit. A series of computer programs, designed for the statistical analysis of monthly data, is developed and a comprehensive analysis of the regional rainfall and streamflow data performed. Regional relationships are developed between rainfall and various streamflow parameters, including monthly means, standard deviations, skewness coefficients, lag-one correlation coefficients and lag-one regression coefficients. The spatial and temporal variation of monthly cross correlation coefficient is investigated and a method of predicting its seasonal variation for any two catchments is presented. Wherever possible the derived relationships are explained in terms of the physical processes involved. Soil moisture is shown to be a key factor influencing both the spatial and temporal variation of several parameters. A soil moisture simulation model is developed and incorporated in a study of the variation of catchment storage and its influence on streamflow. Finally, the derived relationships are used to predict the streamflow parameters for three totally independent catchments, and these are shown to compare very favourably with the corresponding parameters derived from historical records.