Application of linear models for inflow forecasting to the Nyumba ya Mungu reservoir in Pangani river basin in Tanzania
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Date
1997
Journal Title
Journal ISSN
Volume Title
Publisher
university of Dar es Salaam
Abstract
The difficulty in solving practical problems lies mainly in the inability to properly measure or estimate the various hydrologic variables. Reservoir operation, water management and development of water resources above and below the NYM reservoir, requires more accurate assessment of water balance components. The inflow as a hydrologic variable in the water balance equation and operation of the reservoir depends on accurate streamflow forecast which are derived from evaporation, seepage and bank storage to be estimated in magnitude and time distribution. The NYM reservoir regulates river flows for the Pangani falls hydropower systems and other downstream users like irrigation agriculture. Therefore proper management of the water in the reservoir is essential for beneficial utilization of water downstream. The inflow forecasting to the NYM reservoir is considered as contribution from ungauged and gauged catchment. The Linear models MISLM and MILPM were applied in the basin to forecast the inflow to NYM reservoir. The models are of system type and therefore do not consider the underlying mechanism in the transformation of input to output. The MILPM was selected based on better performance in the calibration period and therefore used to forecast the inflow to the reservoir) are based on observed discharges at points further upstream of NYM at IDDI and IDC2A, on the respective main rivers Kikiletwa and Ruvu alone and not on rainfall observed on the intervening catchment. The data used for the study are daily, starting based on hydrological year and the period of record for the study are daily, starting based on hydrological year and the period of record for analysis. More than half of the data lenth was used for model calibration and the remaining serve for verification. The model parameters are optimized by least squares technique. Model performance was analyzed by Nash and Sutcliff efficiency formula based on observed and estimated flows. The obtained results of the model efficiency indicate the adequacy of the linear model to forecast inflow to NYM reservoir. The forecasted inflow were used in the water balance equation to estimate the loss of water in the reservoir as a result of evaporation, seepage and bank storage.
Description
Available in print form, EAF Collection, Dr. Wilbert Chagula Library, (THS EAF TC515.M8)
Keywords
Water balance (hydrology), Sream measurements
Citation
Mulungu, D.M.M (1997) Application of linear models for inflow forecasting to the Nyumba ya Mungu reservoir in Pangani river basin in Tanzania, Masters dissertation, University of Dar es Salaam, Dar es Salaam