Hydrological modelling uses modern computational methods to simulate local and regional water circulation systems. How does this work, and what benefits does it bring?

This study tried to assess the impact of climate change on water resources of the upper Awash River sub- basin (Ethiopia) using a statistical downscaling model (SDSM). The future climatic parameters (rainfall, maximum and minimum temperatures) were generated by downscaling outputs of HadCM3 (Hadley Centre Coupled Model, ver-sion 3) general circulation model to watershed level for A2a (medium-high) and B2a (medium-low) emission scenarios at representative stations (Addis Ababa, Ginchi and Bishoftu). These SDSM generated climatic data were used to develop current/baseline period (1971–2010) and future climate change scenarios: 2020s (2011–2040), 2050s (2041– 2070) and 2080s (2071–2099). The projected future rainfall and mean monthly potential evapotranspiration at these stations were weighted and fed to HBV hydrological model (Hydrologiska Byråns Vattenbalansavdelning model) for future stream flow simulation. These simulated future daily flow time series were processed to monthly, seasonal and annual time scales and the values were compared with that of base period for impact assessment. The simulation result revealed the possibility for significant mean flow reductions in the future during Summer or “Kiremt” (main rainy season) and apparent increase during “Belg” or winter (dry season). Autumn flow volume showed decreasing trend (2020s), but demonstrated increasing trend at 2050s and 2080s. A mean annual flow reduction (ranging from 13.0 to 29.4%) is also expected in the future for the three studied benchmark periods under both emission scenarios. Generally, the result signals that the water resources of upper Awash River basin will be expected to be severely affected by the changing climate. Therefore, different adaptation options should be carried out in order to reduce the likely impact and ensure water security in the sub-basin.

This research addresses the growing complexity and urgency of climate change’s impact on water resources in arid regions. It combines advanced climate modelling, machine learning, and hydrological modelling to gain profound insights into temperature variations and precipitation patterns and their impacts on the runoff. Notably, it predicts a continuous rise in both maximum and minimum air temperatures until 2050, with minimum temperatures increasing more rapidly. It highlights a concerning trend of decreasing basin precipitation. Sophisticated hydrological models factor in land use, vegetation, and groundwater, offering nuanced insights into water availability, which signifies a detailed and comprehensive understanding of factors impacting water availability. This includes considerations of spatial variability, temporal dynamics, land use effects, vegetation dynamics, groundwater interactions, and the influence of climate change. The research integrates data from advanced climate models, machine learning, and real-time observations, and refers to continuously updated data from various sources, including weather stations, satellites, ground-based sensors, climate monitoring networks, and stream gauges, for accurate basin discharge simulations (Nash–Sutcliffe efficiency – NSE _RCP2.6 = 0.99, root mean square error – RMSE _RCP2.6 = 1.1, and coefficient of determination R ² _RCP2:6= 0.95 of representative concentration pathways 2.6 (RCP)). By uniting these approaches, the study offers valuable insights for policymakers, water resource managers, and local communities to adapt to and manage water resources in arid regions.

The Drentsche Aa catchment in The Netherlands, which has nearly untouched natural river valleys, is a designated Natura 2000 area. Agriculture is practiced on the adjacent higher-lying ground. A set of measures was drafted to achieve climate-proof solutions in the short term by reducing the effects of a drier climate on nature and agriculture. These measures must have no adverse effects. In order to check this, the Hunze and Aa’s Water Board investigated the feasibility of using groundwater for sprinkler irrigation in parts of the catchment. In the study, the SIMulation of GROundwater and surface water levels (SIMGRO) hydrological model was used in order to model future scenarios with different water level strategies and climate scenarios. The modelling examined various measures in the nature and agricultural areas to optimise the hydrological situation for both land use functions. In addition, the effect on the nature areas of abstracting groundwater for irrigation was determined for buffer zones of different widths. The findings have indicated the policy direction to be taken by both the water board and the province, as well as offer them opportunities to deal with the requests for withdrawals in the near future by the means of future-proof general rules.