• Energy Research

AbstractIn this study the theoretical hydropower potential of all rivers in West Africa was assessed. The study domain covers 5 Mio km2. For more than 500,000 river reaches the theoretical hydropower potential was computed from channel slope and mean annual discharge simulated by a water balance model. The model was calibrated with observed discharge at 410 gauges, using precipitation and potential evapotranspiration data as inputs. Possible changes in future discharge were assessed by driving the water balance model with climate projections of 15 Regional Climate Models for two emission scenarios of the CORDEX-Africa ensemble.

AbstractStudy regionThe Zambezi River basin (1.4×106 km2) in southern Africa, which is shared by eight countries and includes two of the World's largest reservoirs.Study focusImpacts on future water resources in the Zambezi basin are studied, based on World Bank projections that include large scale irrigation and new hydropower plants. Also the impacts of climate change scenarios are analysed. Modelling challenges are the large basin area, data scarcity and complex hydrology. We use recent GPCC rainfall data to force a rainfall-runoff model linked to a reservoir model for the Zambezi basin. The simulations are evaluated with 60 years of observed discharge and reservoir water level data and applied to assess the impacts on historical and future discharges.New hydrological insights for the regionComparisons between historical and future scenarios show that the biggest changes have already occurred. Construction of Kariba and CahoraBassa dams in the mid 1900s altered the seasonality and flow duration curves. Future irrigation development will cause decreases of a similar magnitude to those caused by current reservoir evaporation losses. The discharge is highly sensitive to small precipitation changes and the two climate models used give different signs for future precipitation change, suggestive of large uncertainty. The river basin model and database are available as anopen-online Decision Support System to facilitate impact assessments of additional climate or development scenarios.

The Zambezi River Basin in southern Africa is relatively undeveloped from both a hydropower and irrigated agriculture perspective, despite the existence of the large Kariba and Cahora Bassa dams. Accelerating economic growth increases the potential for competition for water between hydropower and irrigated agriculture, and climate change will add additional stresses to this system. The objective of this study was to assess the vulnerability of major existing and planned new hydropower plants to changes in climate and upstream irrigation demand. Our results show that Kariba is highly vulnerable to a drying climate, potentially reducing average electricity generation by 12 %. Furthermore, the expansion of Kariba generating capacity is unlikely to deliver the expected increases in production even under a favourable climate. The planned Batoka Gorge plant may also not be able to reach the anticipated production levels from the original feasibility study. Cahora Bassa’s expansion is viable under a wetting climate, but its potential is less likely to be realised under a drying climate. The planned Mphanda Nkuwa plant can reach expected production levels under both climates if hydropower is given water allocation priority, but not if irrigation is prioritised, which is likely. For both Cahora Bassa and Mphanda Nkuwa, prioritising irrigation demand over hydropower could severely compromise these plants’ output. Therefore, while climate change is the most important overall driver of variation in hydropower potential, increased irrigation demand will also have a major negative impact on downstream plants in Mozambique. This implies that climate change and upstream development must be explicitly incorporated into both project and system expansion planning.

The data contains vulnerability estimates (climate niche factor analysis) for 49 native fish species in the upper Danube River basin. The upper Danube River basin is mainly located in Germany and Austria. The time frame covered is 300 years from 1800 to 2100 including two Representative Concentration Pathways, RCP 4.5 and RCP 8.5. Vulnerability estimates are calculated for three time frames (1800-1830; 1900-1930and 2070-2100 (including two RCPs)) with the time frame 1970-2000 as the baseline. In all files the zone column gives the basin ID for the master basins layer. The mean column gives the mean vulnerability estimate for a sub-basin for a certain species. For the future scenarios the different predictions based on the different GCM-RCM combinations have to be combined using the median and the zone as unique identifier.

AbstractAimRivers belong to the most threatened ecosystems on Earth. Historical anthropogenic alterations have, and future climate change will further affect rivers and the species therein. While many studies have projected climate change effects on species, little is known about the severity of these changes compared to historical alterations. Here, we used a unique 300‐year time series of hydrological and climate data to explore the vulnerability of 48 native fish species in the upper Danube River Basin to past and potential future environmental changes.LocationUpper Danube River Basins (Germany and Austria).MethodsWe applied a climate niche factor analysis and calculated species‐specific vulnerability estimates based on modelled and observed hydrological and climate data from 1800 to 2100. We compared the estimated species vulnerabilities between two historical time intervals (1800–1830 and 1900–1930) and a future time interval (2070–2100, including the two representative concentration pathways 4.5 and 8.5) to an observed reference time interval (1970–2000). In addition, we identified the main environmental drivers of species vulnerability and their change over the past 200 years and for the predicted 100 years in the future.ResultsOur results showed that (i) in the past, species vulnerability was mainly driven by changes in discharge, while (ii) future potential vulnerabilities would be due to temperature. Moreover, we found that (iii) future environmental conditions for riverine fish species driven by temperature would change at a similar magnitude as past hydrological changes, driven by anthropogenic river alterations. Future changes, projected for the RCP 4.5, would result in moderate species vulnerability, whereas for the RCP 8.5, the vulnerability for all species would substantially increase compared to the historical conditions.Main ConclusionAccounting for an extended timeline uncovers the extent of historical pressures and provides unprecedented opportunities to proactively plan conservation strategies that are necessary to address future challenges.

AbstractIn the Zambezi basin in Mozambique, hydropower production is an important economic resource, with substantial development envisaged for the next decades. Irrigated agriculture currently plays a minor role, but irrigation development has a large potential and is an important government policy goal, especially aiming at the cultivation of biofuel crops. This contribution assesses interrelations and trade-offs between these two water-dependent development options. Scenario simulations under different climate and development assumptions show that adverse impacts of irrigation withdrawal on hydropower are low. Consequently, the use of water for irrigated agriculture can generate higher economic benefits than the use for hydropower production.

Hydropower represents about 20% of sub-Saharan electricity, and expansion is underway. Rainfall varies year-to-year in geographical clusters, increasing the risk of climate-related electricity supply disruption in dry years.