SOUTHEASTERN ETHIOPIA
Chapter 2: Literature Review
2.2. Climate Change Impacts on the Hydrology and Water Resources 1. Climate change impacts on the hydrologic cycle
2.2.2. Climate change impacts on the water resources management
Vano et al. (2010) studied the effects of climate change impacts on water management and irrigation in the Yakima River Basin, Washington, USA using the Variable Infiltration Capacity (VIC) macro-scale hydrology model from the ensembles of different CMIP4 GCM models under the two IPCC SRES scenarios. They found that earlier snowmelt results in increased water delivery curtailments. Historically, the basin experienced substantial water shortages in 14% of years. Without adaptations, for A1B emission scenarios, water scarcity increases by 27, 33 and 68% in the 2020s, 2040s, and 2080s respectively. For B1 emissions scenarios, shortage tends to rise by 24, 31 and 43% in the 2020s, 2050s, and 2080s respectively. In India, Pakistan, Nepal and Bangladesh, water scarcity has attributed to issues due to rapid urbanization and industrialization, population growth and inefficient water use, which are all aggravated by climate impacted changes induced on demand, supply, and water quality. The decreased precipitation and increased temperature have been reported to increase
water shortages, particularly in parts of Asia where water resources are already under stress from growing water demands and inefficient water use (Manton et al., 2001).
The climate impact assessment has been performed by Vetter et al. (2013) for three river basins on three continents (Rhine in Europe, Upper Niger in Africa and Upper Yellow in Asia) using three hydrological models (HBV, SWIM and VIC) from five CMIP5 GCMs outputs (HadGEM2-ES, IPSL-CM5ALR, MIROC-ESM-CHEM, GFDL-ESM2M and NorESM1-M) which have been downscaled by trend-preserving bias-correction method with the WATCH reanalysis data and have been re-sampled on a 0.5°x0.5° grid (Hempel et al., 2013) for the RCP 8.5 were provided for this study. They found that the uncertainty resulting from climate models is larger compared to that of the hydrological models for all three basins. The impact of climate change on streamflow has been investigated (Liu et al., 2011) using SWAT model from HadCM3 GCM model under the B2 emission scenario which has been downscaled by SDSM in the headwater catchment of the Yellow River basin. The results revealed that an overall decreasing trend in annual streamflow in the headwater catchment of the Yellow River watershed in the 2020s, 2050s, and 2080s time slices was observed.
The impact of climate change on the water resources of twelve river basins in Indian River systems has been studied (Gosain et al., 2006) using SWAT from HadRM2 model under the GHG scenarios. The results revealed that severity of droughts and intensity of floods in various parts of the country might get worsened. Moreover, a general drop of the available runoff has predicted under the future climate scenario. Hydrological changes and its impact on water resources of Bagmati watershed in Nepal has been investigated (Sharma and Shakya, 2006). Due to climate change effect in Bagmati watershed, precipitation during monsoon decreased, and pre and post-monsoon rain increased, but mean yearly flow in river decreased, magnitude of flood decline but frequency and duration of flood increased.
Hydropower generation reduction and concentration of pollution increased because of less water availability. Due to the increasing demand and dropped supply, water conflicts between India and Nepal are likely to increase in future. It has suggested that a proper modality of water sharing should design in advance.
Implications of climate change for sustainable water resources management in India has been reviewed (Mujumdar, 2008). The main findings of this review indicated that the severe water scarcity in one region and flood hazards in other areas has observed, and these affects mainly
water quality and agriculture, so he suggested that the research studies integrating the atmospheric and hydrological models to understand the climatic influence on hydrologic extremes are needed in the country.
The impact of climate and land use changes on the flood hazard of the middle Brahmaputra reach, India was studied (Ghosh and Dutta, 2012) using a physically based macro-scale distributed hydrological model (DHM), which works on the concept of hydrological similarity classes (HSCs), has been calibrated and validated and then used to assess the possible future changes in the flood characteristics and flood vulnerability of the Brahmaputra basin, India, due to climate and land use changes. The bias corrected climatological data from a regional climate model (RCM) simulation (PRECIS) was used to obtain future changes in flood generation and its propagation through the basin in the projected climatological scenario. After model verification, “best guess” land use change scenarios were used to assess potential changes in flood characteristics. Results show that at the middle reaches of the Brahmaputra, peak discharge increases by a maximum of 9% for land use change scenarios and peak discharge will increase by an average of 21% in the future projected climate change scenario.
According to Arnell (2008); Kundzewicz et al. (2008); Rutashobya (2008) review, the impact of climate change on water availability will knock all the biotic and abiotic surrounding in general. This has assured in some field of areas. For example, agriculture reported by Vermeulen et al. (2012), healthy by Gage et al. (2008), ecology by Eriksen and Watson (2009). De Jong et al. (2000); Freibauer et al. (2004); Jandl et al. (2007); Lasco et al. (2002) (as cited in Sarma et al., 2013) have been conducted research on removal of green cover becoming a matter of global concern, as it can accelerate the adverse impacts of climate change. People coming in search of work generally reside in the hills, as they cannot afford the high cost of land in plains. This has led to deforestation of the hilly area and has resulted in increased surface erosion from the upper catchments. Though sediment and water yield from these degraded watersheds could have been minimized by implementing ecologically sustainable management practices (EMPs), such as grass land, forest land and detention pond, poor economic conditions of the people stands in the way of field implementation. On the other hand, major industries, which can be held responsible for emission of greenhouse gases, can be asked to finance greenery development in the hilly watersheds through implementation of selected EMPs to earn carbon credit for them. And, finally, they suggested
that the climate change impacts on the water resources could have alleviated by implementing EMPs.