Tue. Dec 1st, 2020

The “Water Tower of Asia” and The Gilgit River Basin

Image via researchgate.net

By Amjad Hussain

The mountainous glacial region of Hindukush, Karakoram, and Himalayan (HKH) ranges, often termed as the “Water Tower of Asia”, in the upper Indus Basin and adjoining ranges of Pamirs and Tibetan Plateau make the world’s largest treasure of snow and ice masses outside the polar region.

These glacial clothed regions give birth to the mighty Indus River System, which flows through China (8%), India (39%), Afghanistan (6%), and Pakistan (47%). The glaciers of the HKH ranges contribute around 80% of water flow to the Indus River during summers, while more than 50% to the total annual runoff of the Indus river system in Pakistan. The total catchment area of the Indus basin is around 259,913 Km2 and the catchment area that falls in Pakistan is around 122,160 Km2.

Pakistan has a surface-water driven economy, and the agricultural sector of the country, which has an efficiency of around 50%, consumes more than 90% of the surface water. The consumptive use for agriculture and the domestic/Industrial sector is roughly 115.25 Billion Cubic Meters (BCM). The water needed for the ecosystem is 1.5 BCM while the total non-consumptive use is 11.5 BCM. Rainfall provides around 42 BCM of water to the system but the majority of it is lost because of poor storm drainage infrastructure. The total water usage of the country is approximately 126.75 BCM and the total water available is 217 BCM. That means our water usage efficiency is 58.4 % of the total water available, while the rest is lost in the system due to outdated technology in the agricultural sector and lack of infrastructure to manage the water. Moreover, according to Article III of the Indus Water Treaty, Pakistan has unrestricted access to the Western Rivers that Includes the River Indus that makes the river even more vital to the water dynamics and socio-economic growth of the country.

The biggest contributor to the Indus is River Gilgit nested in the Upper Indus Basin of Pakistan, which is capable of producing approximately 50,000 MW of Hydroelectric power alone. Pakistan is the most significant beneficiary of this Indus River System with a staggering 47% share of the overall Indus Basin Area.  According to estimates, more than 70% of flow of the Indus River System in Pakistan is contributed by the Upper Indus Basin (UIB). The UIB can be further divided into Gilgit-Gahkuch, Ishkoman, Phander, Yasin, Gupis, Hunza, Bagrote sub-basins, and small streams extensions from these basins. All tributaries of these sub-basins join each other at different locations and levels to form the River Gilgit, which finally join the Indus River at HKH conjunction.

Most of the areas in Gilgit consist of bare land (43.2%) and grassland (42.9%). The area covered in permanent snow is roughly 13% and a home to hundreds and thousands of organisms. The water plays an important role in maintaining the ecosystem’s bio-diversity of the whole region. That is the reason extensive studies are required to record the fluctuations in the river networks and water resource dynamics, so that we may understand the impact of water on the environment in depth. Mentioned below is a brief summary of the hydrologic features of the Gilgit basin:

The Gilgit River originates from Shandoor Lake, located in upper Phander, in the Hindukush range at an elevation of 3738 meters. Baha Lake is the main right bank tributary of the Gilgit River which is located near the Handarap and Langar rivers. Yasin, Phander, and Ishkomen Rivers drain into the Gilgit River from the left bank, which is then joined by Hunza River in Gilgit city and then by small tributaries until it joins the Indus River on the confluence of the HKH mountain ranges.

The Gilgit River Basin is situated at a high altitude in Hindukush-Karakoram-Himalaya region between longitudes 72⁰53′30″-73⁰29′15″ E and latitudes 33⁰41′07″-34⁰06′00″ N in the northern outskirts of Pakistan. It is a glacier dominant basin and contributes to the Indus River System in Pakistan, so any change in climate that has an impact on the frozen water resource of Gilgit Basin will eventually affect the inflow of Indus River network throughout Pakistan. The total surface area of Gilgit River Basin calculated at Gilgit River gauging station is about 13000 km2 excluding Hunza with an average elevation of 3997 m. The total number of glaciers in this catchment area is 923 that cover an area of about 860 km2. The mean annual discharge of Gilgit River at Gilgit Gauging station is about 288 m3/s. That means the Gilgit river contributes around 7.5 BCM (Billion Cubic Meters) of water to the River Indus annually. The results may vary with varying climatic conditions and this figure may increase due to global warming and the consequent increase in glacial and snow melt. The mean monthly maximum temperature at Gilgit station ranges between 9.5 and 36.2 and the mean monthly minimum temperature between -2.5 and 18.3 C. The mean annual rainfall is about 134 mm in which 70% is usually received during the summer period from April to September.

The temperatures in the northern outskirt of Pakistan have increased significantly since 1985 and this has adversely impacted the structure of glaciers. In addition, Pakistan is located in the monsoon belt, and receives heavy rainfall annually during summer. Therefore, flooding conditions can deteriorate even more in Gilgit and its adjoining tributaries due to both snow/glacier melt and summer rainfall. According to researchers, the average annual runoff in the Gilgit River will increase by 6.703 % and 177.5% by the end of 21st century. This increase in surface runoff from snow and glacier melting can be disastrous to the downstream basin especially in Punjab and KPK if it is not potentially utilized by planning and development of infrastructure for water storage to harness the efficiency of the overall water system and to mitigate flooding problems. The floods of July-August 2010 in Indus River due to torrential monsoon rains are considered to be one of the worst disasters in Pakistan that affected approximately 20 million people, destroyed homes, crops, and caused widespread infrastructure destruction. One of the major factors for such a widespread destruction apart from unprecedented heavy rainfall, in my opinion, is inefficient water management, unsustainable land management usage, lack of required infrastructure, and poor performance of responsible institutes for forecasting of floods based on Hydrologic data and flood management institutes.

The contributor is a Civil Engineer working as Project Engineer at CGICOP. He is also a post-grad student of Water Resources Engineering and Management at NUST.  

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