Abstract
Abstract. Pakistan is highly dependent on water resources originating in the mountain sources of the upper Indus for irrigated agriculture which is the mainstay of its economy. Hence any change in available resources through climate change or socio-economic factors could have a serious impact on food security and the environment. In terms of both ratio of withdrawals to runoff and per-capita water availability, Pakistan's water resources are already highly stressed and will become increasingly so with projected population changes. Potential changes to supply through declining reservoir storage, the impact of waterlogging and salinity or over-abstraction of groundwater, or reallocations for environmental remediation of the Indus Delta or to meet domestic demands, will reduce water availability for irrigation. The impact of climate change on resources in the Upper Indus is considered in terms of three hydrological regimes – a nival regime dependent on melting of winter snow, a glacial regime, and a rainfall regime dependent on concurrent rainfall. On the basis of historic trends in climate, most notably the decline in summer temperatures, there is no strong evidence in favour of marked reductions in water resources from any of the three regimes. Evidence for changes in trans-Himalayan glacier mass balance is mixed. Sustainability of water resources appears more threatened by socio-economic changes than by climatic trends. Nevertheless, analysis and the understanding of the linkage of climate, glaciology and runoff is still far from complete; recent past climate experience may not provide a reliable guide to the future.
Highlights
The Greek historian Herodotus (5th century BC) described Egypt as “the gift of the Nile” and “as a land won by the Egyptians and given them by the Nile”
The fertility of the alluvial plains of Pakistan derives from sediments deposited over geological time by the Indus from the high mountain ranges of the Himalaya-Karakoram-Hindu Kush (HKH)
The continuing flow of water across the plains is largely derived from the same source and provides the basis for irrigated agriculture which is the mainstay of Pakistan’s economy
Summary
The Greek historian Herodotus (5th century BC) described Egypt as “the gift of the Nile” and “as a land won by the Egyptians and given them by the Nile”. Concerns about the impact of climate change on the Indus, based on an assessment of what might happen, given temperature changes in line with global climate change projections (Rees and Collins, 2005; Akhtar et al, 2008), have given rise to expectations of dramatic decreases in river flow (Briscoe and Qamar, 2007) Such concerns have been supported by reports of significant retreat and depletion of glacier volume across the HKH (Himalaya-Karakoram-Hindukush), (Eriksson, 2009; Berthier, 2007; Shrestha et al, 2004). Hewitt (2005) notes that in the late 1990s there was widespread evidence of glacier expansion mainly in high level glaciers in the central Karakoram Such conflicting views on what changes have occurred in the climate and glaciers of the Upper Indus Basin have serious implications for future water management in Pakistan and for the sustainability of water resources, through the resulting impact on downstream flows reaching the irrigated plains of the Punjab and Sindh. It is necessary to consider how freshwater resources have been, and will be, affected by changes in these non-climatic drivers (Bates et al, 2008)
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