19) in the evaluation period. The most likely source for this bias is that the precipitation inputs are already biased. From the calibration to the evaluation periods mean annual precipitation Smad2 phosphorylation increased by +3%, but observed discharge decreased by −4%. Even though these are small changes, it is counter-intuitive that discharge decreases when
precipitation increases. Here, the low density of precipitation stations has to be considered in the upper Zambezi basin, which is on average approximately one station per 21,000 km2 in the calibration period, but even lower during the evaluation period (see Fig. 2). An under-estimation of discharge in the evaluation period is also obtained at the upstream gauge Lukulu, albeit the period with available data is only 7 years. The under-estimation of Kafue River discharge at the gauge Kafue Hook Bridge during the calibration period is the result of a large negative bias (−34%) during a 5-year period (1978–1982), which coincides with the start of operation of nearby Itezhitezhi reservoir. The source of this bias is not clear, but it could be related to the accuracy of the precipitation data or the discharge data. Outside this 5-year period the simulation shows only a small bias – this also applies to the independent evaluation period. The calibrated model was applied for simulation of a number of pre-defined scenarios (see Table 3). The scenario
simulations are always compared Phosphoribosylglycinamide formyltransferase against the “Baseline” scenario representing current Selleckchem BKM120 water resources management (reservoirs, operation rules, irrigation withdrawals) in the basin but using historic climate of the period 1961–1990. The analysis focuses on Zambezi River discharge at Tete in Mozambique. Table 5 lists mean annual scenario results. Mean annual discharge in the Baseline scenario amounts to approximately 2600 m3/s, with values ranging from around 1750 m3/s to
3700 m3/s in the scenario simulations. Total evaporation losses from reservoirs amount to 437 m3/s in the Baseline scenario. This value ranges from 418 to 499 m3/s in the other scenarios. The differences are caused by: • Different number of reservoirs (Batoka Gorge and Mphanda Nkuwa are included in the Moderate and High development scenarios). More than 90% of the total reservoir evaporation occurs from Kariba and Cahora Bassa reservoirs. These are significant losses of water and the main reason that under the Pristine scenario (with no reservoirs) discharge is considerably larger than in the other scenarios. In addition to the reservoirs, water also evaporates from the natural wetlands and floodplains – with mean annual evaporation losses ranging from 243 to 364 m3/s between the scenarios. The contribution to total evaporation from the individual wetlands is roughly 40% from Kafue Flats, 25% from Barotse Floodplain, 25% from Chobe Swamps, and 10% from Kwando Floodplain.