The Kabul times, Afghanistan Trustable News Agency.
Articles

Water resources of Afghanistan and related hazards under rapid climate warming

Part VII

Studies of snow-dominated basins around the world have suggested that climate warming results in streamflow increases during the accumulation season and during the early melt season, due to seasonal shifts in snow accumulation, snowmelt and the amount of winter rainfall. In arid river basins, where climate change is expected to have a significant impact on snow and ice cover, climate change may have a serious impact on water resources. In Afghanistan, 80% of water resources have some contribution from snow and glaciers, including water required for summer irrigation and hence food production. Therefore, warming in combination with precipitation changes has led to a strong decrease in river discharge for snow-fed basins in Afghanistan. Muhammad et al. (Citation2017) and Casale et al. (Citation2020) showed that winter snowfall was a crucial influence on the likelihood of summer drought in the Afghan lowlands. Glacier meltwater supply also contributes to sustaining summer water availability and aquifer recharge (Gellasch Citation2014). An early study estimated that with a 1°C increase in mean annual air temperature, the amount of glacial meltwater in Afghanistan rivers is likely to decline by as much as 14% (Lebedeva Citation 1997). Scaling this estimate to the current measured increase of 1.8°C, a decline of about 25% should have occurred. Here we consider more precisely changes in river streamflow at national and local scales in Afghanistan. In 2016, the Ministry of Energy and Water reported a mean 13% decrease of river streamflow in five major river basins between the period 1969–1980 and 2007–2016 based on measured hydrological data. By 2030, all of these decreases were expected to continue to amplify. Bromand (Citation2015) studied future streamflow changes in the Kabul River basin, focusing upon the impacts of climate change. Results suggested that with an increase of mean temperature of 2.9°C for the period 2046–2064, the Kabul River basin will experience severe summer water scarcity with a reduction of about 24% in water availability despite, by 2046–2064, a potentially positive precipitation anomaly (Sidiqi et al. Citation2018). Akhtar et al. (Citation2021) also studied the impact of climate change on streamflow in the Kabul River basin using the Soil and Water Assessment Tool (SWAT) hydrological model under RCP 4.5 by 2030. The model predicted an average 4.2% decrease in streamflow, except for the eastern part of the basin where an increase of 2.4% was estimated. The decrease arises from two processes. The first is an increase of 18% in potential evapotranspiration. The second is a reduction of precipitation in spring and winter (Savage et al. Citation 2009, NEPA and UNEP Citation 2016). The Kabul River has no scope to store water (e.g. storage dams) at present and winter streamflow cannot be used for summer crop production. Masood et al. (Citation2020) studied the Kabul River basin farther downstream in Pakistan and indicated an increase in summer streamflow due to larger contribution from snow and ice melt under both RCP 4.5 and 8.5 in the near future (2011–2030), which contradicts the findings of Bromand (Citation2015) and Akhtar et al. (Citation2021). These contradictory findings are most probably related to the hydrological model, SWAT, used by Bromand (Citation2015) and Akhtar et al. (Citation2021), which is not able to simulate the runoff contribution from glaciers (Omani et al. Citation2017, Singh, et al. Citation2021) and may underestimate summer streamflow. In addition to streamflow, there is a general trend towards a decline in water availability; Salehie et al. (Citation2022) assessed equivalent water thickness to provide an estimation of total water availability (groundwater, soil moisture storage, surface water storage, and snow water equivalent) for Panj Amu River basin. The findings suggest a decline in northern Afghanistan by “0.05 to “0.1 cm/ year”1 from 2002 to 2019. Sediqi et al. (Citation2019) showed an even higher decline in the north, of up to “0.44 cm/year, and a decline of up to “3.47 cm/ year (2002 to 2016) in the central region of Afghanistan. In the absence of more detailed studies, we have analyzed daily discharge data from individual gauging stations for six glacierized and one snowrain-fed basin for two time periods (1969–1977) and (2008– 2016) (Fig. 4) to illustrate how glaciated, non-glaciated and snow-dominated basins have responded to climate change. In Afghanistan, due to the history of armed and political conflict, there is a gap in records between 1977 and 2008. Recently, station-wise data became available from the Ministry of Energy and Water of Afghanistan upon request. Figure 4 shows increases in the summer discharge peaks for the glacier-fed basins (Taloqan, Keshelm, Bamyan, Omarz, Nazdik-i-Jurm, Nazdik-i-Baharak) in the period 2008–2016 compared to 1969–1977, implying an increase in glacial melt rate given no consistent trend in summer precipitation (Savage et al. Citation2009, NEPA and UNEP Citation2016, Aich et al. Citation2017). For Dawlatyr (Fig. 4(g)), the one station with no glacial influence, there is a clear reduction in summer daily mean discharges. The peak streamflow for Dawlatyr occurs earlier in the year for the period 2008–2016 than for the period 1970–1978, suggesting an earlier onset and end of snowmelt. For the four most northerly glacier-fed stations (Taloqan, Keshem, Nazdik-i-Bahakrak and Nazdik-i-Jurm), peak flow is displaced to slightly later in the year, although this signal is weaker for Keshem and Nazdik-i-Baharak (Fig. 4(b) and (c)). Reduced spring streamflow would reflect the decreases in spring precipitation reported by NEPA and UNEP (Citation2016) and Aich et al. (Citation2017). Omarz and most notably Bamyan are the stations influenced by the smallest glaciers and at the lowest elevations. They have shown no real change in the timing of the peak streamflow. Streamflow in Bamyan, the lowest in elevation, has increased throughout the year and markedly in winter months. The shift in streamflow is almost systematic, suggesting that there may have been a rating curve shift that is not properly accounted for. This conclusion may apply to all of the data shown here, emphasizing the difficulty of using hydrological records alone in data-poor settings like Afghanistan, in trying to draw clear conclusions about hydrological change. However, the other stations match more directly the expected response to observed climate changes (Fig. 4) and there is no evidence of a systematic shift. Thus, Bamyan may be an anomaly. From: Hydrological Sciences Journal

Related posts

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

The Kabul times, Afghanistan Trustable News Agency.