On the Relation between Hydrological Forecasts and Water Resources Management

Seasonal streams (wadis) are of vital importance in dry and semidry countries including Sudan. Depending on the rainfall variability of the country, the annual discharge of such wadis was estimated to range from 3 to 7 km3 per annum. In the present study two wadi-discharge prediction methodologies were used to predict the discharge of Khor (wadi) Abu Fargha. The first methodology depends on the El Nino Southern Oscillation (ENSO) event which was divided into six distinct stages. The discharge during each stage was compared to previously estimated rainfall in the dry zone of the Sudan during the concurrent stage. The methodology was found to illustrate about 83% of the discharge behaviour of Khor Abu Fargha. This high prediction skill is attributed to the fact that the wadi is located in an area that is influenced by the ENSO event and to the availability of the discharge data for consecutive 34 years. The use of global sea surface temperatures (SSTs) in rainfall seasonal forecast studies was initiated during the 1990s through the development of empirical-statistical models. Using such methodology the models predicting Abu Fargha discharges were found to excel those for some meteorological stations and the dry zone of the Sudan as well. This is attributed to the fact that wadi discharges represent the whole catchment area whereas rainfall data represent only the rain gauge readings. The models using May global SSTs achieved better predictability in Abu Fargha discharges the thing which was found to be consistent with the results obtained in previous studies by Kassala meteorological station which is located in the vicinity of the wadi. The chapter illustrates the use of the wadi prediction information in forecasting the available storage of the aquifers and concluded that combining the different information, realistic management of surface and ground water resources can be achieved. The study recommended the use of water conservation techniques and integrated dryland management approaches.