ISciences has developed the capability to assess risks to electricity production due to the impact of water deficits and temperature anomalies (see "NOTE" below). Water deficits directly limit the ability to produce hydropower and to provide cooling for thermal power generation; and, warm temperature anomalies reduce both the generating and cooling efficiencies of thermal power generation. As with our Water Security Indicator Model (WSIM), this capability operates on a monthly basis and both monitors current stress levels and provides monthly forecasts with lead times of up to nine months. In this blog post, we demonstrate this capability by providing a brief analysis of the current situation in Zambia.
As shown in our monthly WSIM assessments, widespread water deficits are currently affecting large parts of Africa. While these deficits are expected to diminish in most locations, Zambia is forecast to be hit with particularly severe and long lasting deficits until September 2016 (Figure 1).
Figure 1. WSIM Composite index for the past 3 months and 9 month forecast, showing deficits in Zambia extending to September 2016. Based on observed data through Mar 2016 and forecasts issued last week of Mar 2016.
Like many African countries, Zambia is highly dependent on hydroelectric power, with 95% of its electricity coming from a few large dams, especially the Kariba Dam on the Zambezi River, with a capacity of 1080 MW and the Kafue Gorge Dam on the Kafue River, with a capacity of 930 MW (Figure 2).
Figure 2. Locations of major hydroelectric dams in Zambia.
WSIM indicates that the Zambezi and Kafue Rivers at these locations have had very low flow for the past several years (Figure 3). At Kariba Dam, only one year (2014) in the past five has had anything close to a normal wet season. Trends at Kafue Gorge Dam have been similar, but with less severe drought in 2015. As a result, lake levels at Kariba are at or near historic lows. At both locations, abnormally low water levels are forecast to continue at least until the start of the next wet season.
Figure 3. Total blue water (flow accumulated runoff) at Kariba Dam and Kafue Gorge Dam in Zambia. Background colors indicate anomaly of indicated water levels (see key).
These low flows are merely the latest in a succession of abnormally dry years for at least the past decade region wide (Figure 4).
Figure 4. Total blue water (flow accumulated runoff) anomalies for the past decade in southern Africa.
These low water levels have a significant impact on Zambia's electrical supply, as illustrated by ISciences' WSIM electricity assessment (Figure 5). This shows that risk to Zambia’s generating capacity has been quite high for the past 5 years. As of March 2016, losses were projected to be nearly 80% and increasing.
Figure 5. Proportion hydroelectric power lost due to low water levels. Black indicates projections based on observed data, dark blue indicates current forecast, light blue indicates previous month’s forecast.
These estimated losses match those reported in the press. Just this month, the New York Times reported that production at Kariba Dam was at 25% of capacity and power disruptions in Zambia have been widely reported on in the past months (e.g. Quartz and Bloomberg).
[NOTE: ISciences' WSIM electricity assessment is produced monthly and shows estimated power losses globally for the past three months and forecast for the next nine months, by country, state/province, distribution grid, and watershed. The assessment combines WSIM data on flow accumulated runoff (total blue water) and temperature with data on electrical plant location and characteristics such as generating capacity, fuel stock, and cooling type to produce an estimate of generating capacity loss due to low water levels or high temperatures. In addition to present and forecast data, historical assessments are available going back to 1990.]
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