اکتوبر 01, 2016
Pakistan will reach ‘absolute water scarcity’ and will ‘run dry’ by 2025 are two popular expressions that have been circulating in world media over the past six months. These expressions are typically followed by strong advocacy for the Basha dam and other large storages. The advocates for the Basha dam in particular have been the Supreme Court of Pakistan and the newly elected government, Imran Khan’s Pakistan Tehreek-e-Insaaf (PTI). Moreover, the importance given to the Basha dam has been so significant that the Supreme Court and the government have jointly initiated a crowdsourcing drive (probably the first of its kind on this scale), requesting Pakistani citizens to fund the multi-billion dollar mega project.
Many Pakistanis have responded positively to this request and are contributing to the dam fund. There are many stakeholders though, who have reservations on development of the Basha dam, or any other large storage within the Indus basin. For instance, people of Sindh have historically had serious reservations regarding construction of large surface storage reservoirs, primarily due to their potential catastrophic impact on the Indus delta. If there is more water upstream, less will flow into the delta, drying up the region, and severely affecting the coastal communities of Sindh. It seems though that the public opinion is in favor of Basha, maybe because people are fearful of the country’s impending ‘absolute water scarcity’. Yet, do we fully understand the meaning of ‘absolute water scarcity’? Furthermore, do we understand the role of Basha dam and other large storages in tackling our water scarcity challenges?
The term ‘absolute water scarcity’ actually has two distinct formal definitions. According to the Falkenmark Indicator, ‘absolute water scarcity’ is reached when a country has less than 500 cubic meters of water available per capita. This definition is hard to comprehend without knowing the per capita water demand of a country. For instance, countries like Singapore and the UAE have per capita water availabilities that are significantly below the, ‘absolute water scarcity’ thresholds. However, since these countries have insignificant agricultural water demands, their water availability levels are sufficient for other consumptive uses such as drinking water, domestic demands, and industrial demands.
Pakistan on the other hand is an agricultural-centric economy (the Falkenmark Indicator was developed bearing Israel, a developed country with a highly industrialised economy, in mind) and hence, has a significantly higher water demand (per capita) than Singapore and UAE. This is where the second definition of ‘absolute (or physical) water scarcity’ becomes relevant. According to the International Water Management Institute (IWMI), ‘physical (or absolute) water scarcity’ is reached when a country’s water demands – both human and environmental – exceed its available renewable water. A recent analysis published in UNDP’s Development Advocate Pakistan (DAP) (Issue 3, Volume 4) reports that Pakistan is already extracting more than 74% of its renewable water resource annually. It is highly likely that this extraction/availability percentage estimate is based on average annual water availability, but what about drought years?
Today’s reality of Climate Change and the natural variability of river flows mean that annual freshwater availability (in most river basins) can vary dramatically. This is the reason why the Indus basin experienced massive flooding in the 2010-11 water year with total freshwater availability exceeded 150 Million Acre Feet (MAF). The droughts of 2000-01 were the other extreme of the variability spectrum, and freshwater availability was less than 100 MAF in 2000-01. The net annual crop water demand of Pakistan’s Indus Basin Irrigation System (IBIS) alone is around 100 MAF. Pakistan’s agricultural demand (excluding conveyance and field losses) is around 90% of total consumptive demand. Hence, assuming that an additional 10-15 MAF may be required for domestic, industrial and environmental use (environmental flow requirements to the Arabian Sea may be more than 10 MAF per annum), Pakistan’s current water demand may easily exceed the water availability in a drought year – as was the case in 2000-01. If such drought conditions are encountered in the future, and for extended periods, Pakistan will indeed face ‘physical (absolute) water scarcity’.
This is where new large storage dams like Basha can be extremely important. They can assist our water decision makers in providing surplus water supplies (stored in non-drought years) in extended drought periods. According to a recent analysis conducted by the Pakistan Council of Research in Water Resources (PCRWR), the country is likely to experience an extended drought by 2025. In-fact the current year, 2017-18, is a drought year. The Basha dam makes eminent sense in the context of sustaining the country through such droughts.
Is Pakistan ready to manage drought?
However, is our current reservoir management framework equipped to use Basha effectively during extended periods of drought? Are drought predictions incorporated into the management of our current reservoirs? Management of the Mangla reservoir during the 2017-18 drought seems to indicate that we are not equipped to manage our reservoirs during droughts.
The reservoir management framework in Pakistan follows a very familiar pattern every year. Our two current large storages, i.e., Tarbela and Mangla, are filled during the wet season of Kharif, from April to September (and mostly during June-August), and emptied during the dry season of Rabi, October to March – primarily, to fulfil water requirements for wheat production. Since both dams are filled and subsequently emptied within a year, they cannot really hedge us during drought years.
This management phenomenon is understandable for Tarbela reservoir, that has lost more than 30% of its storage capacity since inception, and hence, has to consume its entire storage for irrigation demand in every Rabi season. However, the story for Mangla is different. Mangla dam was raised in 2009 that increased the storage capacity of its reservoir by more than 50%. The added storage should have given the reservoir managers an opportunity to change its filling pattern, and carryover its storage over multiple years to hedge for drought periods. However, even after a significant increase in storage capacity, the management of Mangla has continued to follow the within-year fill-and-empty pattern. A consequence of this static management pattern is that the current storage (at the start of the current Rabi season) of Mangla stands at less than 40% of its capacity.
Rethinking reservoir strategies
The significant annual uncertainties of river flows in the Indus Basin demand a rethink of our reservoir management and operations strategies. But can we predict these uncertainties in advance? Recent advances in satellite-based hydrological predictions and geospatial data analytics indicate that concrete indicators of seasonal water availability predictions such as snow cover area and glacial extents can be estimated, and algorithms for these estimations for Upper Indus Basin are available. Hence, predictions of droughts are possible, and should be used by reservoirs managers in Pakistan to hedge for droughts.
It is high time that our reservoir managers incorporate these technological advances into their decision-making process, and showcase a well-informed, dynamic and creative reservoir management thought process. Only then can we attempt to tackle our future water challenges. Only then, we may deserve to spend billions of dollars on building new large storages.
The writer is a researcher and consultant in water resources systems engineering and management. He has a PhD from Cornell University and is currently a Research Fellow at National University of Singapore and can be contacted at: [email protected]
 Pakistan’s per capita water demand is at least 5 times greater than Singapore’s (primarily due to agriculture)