Climate Change: Implications and Adaptation of Water Resources in Pakistan

Transcription

1 Research Report GCISC RR 13 Climate Change: Implications and Adaptation of Water Resources in Pakistan Ghazanfar Ali, Shabeh ul Hasson Arshad M. Khan June 2009 Global Change Impact Studies Centre Islamabad, Pakistan

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3 Research report GCISC RR-13 Climate Change: Implications and Adaptation of Water Resources in Pakistan Ghazanfar Ali, Shabeh ul Hasson Arshad M. Khan June, 2009 Global Change Impact Studies Centre (GCISC) National Centre for Physics (NCP) Complex Quaid-i-Azam University Campus P.O.Box 3022, Islamabad, Pakistan

4 Published by: Global Change Impact Studies Centre (GCISC) National Centre for Physics (NCP) Complex Quaid-i-Azam University Campus P.O. Box 3022, Islamabad Pakistan ISBN: GCISC Copyright. This Report, or any part of it, may not be used for resale or any other commercial or gainful purpose without prior permission of Global Change Impact Studies Centre, Islamabad, Pakistan. For educational or non-profit use, however, any part of the Report may be reproduced with appropriate acknowledgement. Published in: June 2009 This Report may be cited as follows: Ali, G., S. Hasson, and A.M. Khan, (2009), Climate Change: Implications and Adaptation of Water Resources in Pakistan, GCISC-RR-13, Global Change Impact Studies Centre (GCISC), Islamabad, Pakistan.

5 C O N T E N T S Foreword Preface List of Tables List of Figures List of Acronyms i ii iii iv v 1. Introduction 1 2. Water Resources of Pakistan 2 3. Hydrology of the Indus Basin 4 4. Key Vulnerabilities of Pakistan s Water Resources Deglaciation Worldwide Glaciers Retreat Himalayan Glaciers Retreat Impacts of Deglaciation Worldwide Himalayan Region Increased Variability in River Flows 8 5. Analysis of IRS Flows in context of Glacier Recession & Temperature Increase Trend of Historical Flows Projected Flows of Indus River using 12 UBC Watershed Model 6. Adverse Impacts and Adaptation Measures Major Concerns Floods Glaciers Lakes Outburst Floods (GLOF) Droughts Sea Water Intrusion Sedimentation and Loss of Reservoir Capacity Shrinking Wetlands Groundwater Depletion Water Logging and Salinity 21

6 6.10 Increased Water Demand Need for Policy Development and Recommendations Integrated Planning and Development of Water Resources Groundwater Flood & Drought Management Trans-boundary Water Sharing Recommendations 24 References 26

7 F O R E W O R D Global Change Impact Studies Centre (GCISC) was established in 2002 as a dedicated research centre for climate change and other global change related studies, at the initiative of Dr. Ishfaq Ahmad, NI, HI, SI, the then Special Advisor to Chief Executive of Pakistan. The Centre has since been engaged in research on past and projected climate change in different sub regions of Pakistan; corresponding impacts on the country s key sectors; in particular Water and Agriculture; and adaptation measures to counter the negative impacts. The work described in this report was carried out at GCISC and was supported in part by APN (Asia Pacific Network for Global Change Research), Kobe, Japan, through its CAPaBLE Programme under a 3-year capacity enhancement cum research Project titled Enhancement of national capabilities in the application of simulation models for assessment of climate change and its impacts on water resources, and food and agricultural production, awarded to GCISC in 2003 in collaboration with Pakistan Meteorological Department (PMD). It is hoped that the report will provide useful information to national planners and policymakers as well as to academic and research organizations in the country on issues related to impacts of climate change on Pakistan. The keen interest and support by Dr. Ishfaq Ahmad, Advisor (S & T) to the Planning Commission, and useful technical advice by Dr. Amir Muhammed, Rector, National University for Computer and Emerging Sciences and Member, Scientific Planning Group, APN, throughout the course of this work are gratefully acknowledged. Dr. Arshad M. Khan Executive Director, GCISC i

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9 P R E F A C E Fresh water resources are among the sectors that are most vulnerable and have potential to be strongly impacted by the changing climate. There is ample evidence supporting this statement both by observational records and the climate projections. According to IPCC Fourth Assessment Report 2007, the frequency and intensity of extreme climatic events are expected to increase over the coming decades. This may cause serious impacts on the intensity, frequency and distribution of precipitation spells on temporal and spatial scales; accelerate melting of glaciers and increase number and intensity of floods and droughts. Potential direct impacts of climate change include highly variable pattern of seasonal inflows to water reservoirs, water shortage for agriculture, insufficient recharge of ground water and sea level rise which coupled with sharp decrease in per capita water availability due to ever increasing population, may cause serious implications for water resources management. These impacts may get more severe where the management practices are not developed fast enough to face the challenges. Like many other developing countries in the South Asia region, Pakistan s long-term water availability and power generation rest on continued flow from the rivers of the Indus Basin originating from the Hindu Kush-Karakoram-Himalaya (HKH) mountain ranges. It is indeed very difficult to predict future changes in weather patterns on regional level or to assess the real impact of climate change on water resources. However, geographical location of Pakistan places the country in heat surplus zone on the earth making it very high on vulnerability scale on weather changes. The phenomenon of glacier retreat is of particular concern to Pakistan as rivers of the Indus Basin receive up to 80% of their flows from snow and glacier melt. This report is an effort to identify some possible threats to water resources in Pakistan under changing climate and to put forward some recommendations to address the adverse projected impacts/implications effectively so that these could be minimized by adopting appropriate strategies. ii

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11 List of Tables Table 1 Percentage Contribution of Indus River System (IRS) Rivers 5 Table 2 Live Storage Capacity of Pakistan of iii

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13 List of Figures Figure 1 Layout of Indus River System Network 3 Figure 2 Indus Basin Irrigation System (IBIS) 4 Figure 3 Annual Flow Variations of the Indus at Kalabagh 9 Figure 4 Escapage to Sea down below Kotri 9 Figure 5a Trend in Annual Inflows of Indus at Kalabagh 10 Figure 5b Trend in Annual Inflows of Indus at Tarbela. 11 Figure 5c Trend in Annual Inflows of Jhelum at Mangla 11 Figure 5d Trend in Annual Inflows of Chenab at Marala 12 Figure 5e Trend in Annual Inflows of Kabul at Nowshera 12 Figure 6 Mean Monthly Flows for the Period of Record Figure 7 Decadal Flood Frequency in Pakistan 15 Figure 8 Number of Floods Recorded in Each Year ( ) with a Quadratic Trend 15 Figure 9 Loss of Storage Capacity of Three Major Reservoirs and Total 20 iv

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15 List of Acronyms IPCC AR4 HKH MAF IBIS UIB IRS IRSA WGMS WGHG GHG UBC GCISC GLOF FFC WAPDA DMP Intergovernmental Panel on Climate Change IPCC, Fourth Assessment Report Hindukush - Karakoram - Himalaya Million Acre Feet Indus Basin Irrigation System Upper Indus Basin Indus River System Indus River System Authority World Glacier Monitoring System Working Group on Himalayan Glacier Green House Gases University of British Columbia Global Change Impact Studies Centre Glacial Lake Outburst Flood Federal Flood Commission Water and Power Development Authority Draining Master Plan

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17 Climate Change: Implications and Adaptations of 1. Introduction Water Resources in Pakistan The continuous increase in emission of greenhouse gasses has resulted in global warming, and substantial changes in the future climate are expected by the end of the current century. Global average temperatures have been rising, and human activities have changed the composition of the atmosphere significantly enough that we can now confidently say that the climate will continue to change. Along with the projected future increase in temperature by o C (IPCC AR4) by the end of year 2100, there will be changes in atmospheric and oceanic circulation, and in the hydrologic cycle, leading to large increases in frequency and intensity of extreme climate events such as floods, droughts and cyclones; rapid melting of world s glaciers and ice sheets including the polar ice; rise in average sea level causing submersion of small islands and other low lying coastal areas etc. Particularly large will be the adverse impacts of climate change on developing countries like Pakistan whose water and food security could be threatened by the climate change. In the past few decades, global climate change has had a significant impact on the high mountain environment: snow, glaciers and permafrost are especially sensitive to changes in atmospheric conditions because of their proximity to melting conditions. In fact, changes in ice occurrences and corresponding impacts on physical conditions high-mountain system could be one of the most directly visible phenomena of temperature increase. This is also one of the primary reasons why glacier observations have been used for climate system monitoring for many years (Haberli 1990). The warming observed over the past several decades is consistently associated with changes in the hydrological cycle such as: increasing atmospheric water vapor; changing precipitation patterns, intensity and extreme events; widespread melting of snow and ice; and changes in soil moisture and runoff. Projected Global temperatures will also likely to alter the hydrologic cycle in ways that may cause substantial impacts on water resource availability and changes in water quality. For example, the amount, intensity, and temporal distribution of precipitation are likely to change. Warmer temperatures will affect the proportion of winter precipitation falling as rain or snow. Long term climatic trends could also bring changes in vegetation cover that would alter a region s water balance. In addition, changes in the quantity of water percolating to the groundwater storage will result in significant changes in aquifer levels, in base flows entering surface streams, and in seepage losses from surface water bodies to the groundwater system. IPCC, 2007 reported that by the mid-century, annual average river runoff and water availability will increase by 10-40% at high latitudes and in some wet tropical areas, and decrease by 10-30% over some dry regions at mid-latitudes and in the dry tropics. Similarly, water supplies stored in glaciers and snow cover are projected to decline during the 21 st century, thus reducing water availability in regions supplied by melt water from major mountain ranges, where more than onesixth of the world population currently live. Like many other developing countries in the region Pakistan, which lies between 24 o 38 o N and 61 o - 78 o E, gets most of its fresh water supply from snow and ice melt in the mountain regions that may be affected by the climatic changes in many 1

18 ways. This is particularly critical for Pakistan as its long term water availability and power generation rest on continued flow from the rivers of the Indus Basin originating from the Hindu Kush-Karakoram-Himalaya (HKH). It is indeed very difficult to predict future changes in weather patterns on regional level or to assess the real impact of climate change on water resources. However, geographical location of Pakistan places the country in heats surplus zone on the earth making it very high on vulnerability scale on weather changes. Before discussing the implication and adaptation measures it is imperative to understand the country s major resources of melt water and their hydrology. 2. Water Resources of Pakistan The surface water hydrology of Pakistan is dominated by the Indus River and its five major tributaries; Kabul, Jhelum, Chenab, Ravi and Sutlej. The Indus River system resembles a funnel with a number of water resources at the top converging into a single river that flows into the Arabian Sea (Fig.1). Under the 1960 Indus Basin Treaty between India and Pakistan, Pakistan is entitled to the flow of three western rivers (Indus, Jhelum and Chenab) with occasional spills from the eastern rivers Sutlej and Ravi diverted up stream by India. The flow of rivers under Pakistan control are mainly depend upon snow and glacier melt except Jhelum River, which also receives rainwater under monsoon system during summer. The average annual flows of the western and eastern rivers and their tributaries at the rim stations is 142 Million Acre feet (MAF) in which main Indus River contributes more than 45% of these average annual flows. The rainfall in Pakistan is low as half of the country receives less than 200 mm of annual rainfall. Most of the rainfall occurs during the monsoon season. Both the intensity and volume in monsoon season are erratic and cannot be utilized by crops production. The groundwater aquifers of the Indus Plains are the second major source of freshwater and are mainly recharge by the precipitation, the river flows, and the seepage from the canal systems, distributaries, watercourses and application losses in the irrigated fields. These vast aquifers of freshwater are being exploited to an extent of about 40 MAF through pumping for agriculture, industrial and domestic usage. Pakistan is basically an agrarian country with a population of 160 million dependent upon the irrigated agriculture in the Indus Plains. This is served through the world s largest contiguous irrigation system in the Indus Basin developed over the last 150 years or so (Fig. 2). The system comprises three major reservoirs (Tarbela, Mangla and Chashma) and 16 barrages, 2 head-works, 2 siphons across major rivers, 12 inter river link canals, 44 canal systems (23 in Punjab, 14 in Sindh, 5 in NWFP and 2 in Balochistan) and more than 107,000 water courses. The aggregate length of the canals is about 56,073 km. In addition, the watercourses, farm channels and field ditches cover another 1.6 million km. The system utilizes over 41.6 MAF of groundwater, pumped through more than 500,000 tube wells, in addition to the canal supplies. 2

19 The Indus River Basin, Pakistan The Indus River System, Pakistan Figure 1: Layout of Indus River System Network 3

20 Figure 2: Indus Basin Irrigation System (IBIS) Source: IUCN Pakistan Water Gateway, Irrigation System in Pakistan, 3. Hydrology of the Indus Basin The hydrological system of the Indus Basin is complex. It combines runoff from glaciers, snowmelt and rainfall. It is further complicated by variable snow cover in space and time and by upward migration of melting temperatures with altitude. Glacier melt is the largest component of water supply in Indus River whereas combined water from glacier melt and snowmelt dominate flow for Chenab and Kabul rivers. The Jhelum River is mainly fed by snowmelt and rain water under summer monsoon system. These rivers originate in mountains with elevations ranging from 4500 to 7500 meters above sea level (m.a.s.l). The tremendous arc of the Karakoram Mountains, which extends over 350 km, holds the greatest concentrations of snow and glacier ice on the Asian mountains (Hewitt 1986). Melt water from these glaciers is the largest component of water supply in the rivers of the Upper Indus Basin (UIB). An estimate shows that snow and glacier melt contribute up to 80% to the annual flows. The melting starts in early March in some basins and in April in others and continues throughout the summer. River flow consists mostly of snowmelt until early July after that glacier melt becomes a major factor under the influence of monsoonal air masses. However, in August heavy rainfall is usually reduced considerably as the air masses 4

21 originating from Bay of Bangal and Arabian Sea either loose their moisture in greater Himalayas or rarely penetrate to the northwestern parts of the Himalayas. The relative percentage contributions of these rivers and the major sources of input are shown in Table 1. Table 1: Percentage Contribution* of Indus River System (IRS) Rivers Name of River %of IRS Inflows % Seasonal Distribution Dominant April to September October to March Source in Summer Indus Jhelum Chenab Kabul Snow/Glacier Snow/Monsoon Snow/Monsoon Snow/Glacier Others 5 *Based on Data for Rivers Flowing in Pakistan Dominant Source in Winter Winter Rainfall + Baseflow Winter Rainfall + Baseflow Winter Rainfall + Baseflow Winter Rainfall + Baseflow 4. Key Vulnerabilities of Pakistan s Water Resources According to the IPCC Technical Paper on Climate Change and Water, Asia is the region where water distribution is uneven and large areas are under water stress. Decreasing trends in annual mean rainfall were observed in Russia, North China, the coastal belt and arid plains in Pakistan, parts of northeast India, Indonesia, the Philippines and some areas in Japan. In addition, inter seasonal, inter-annual and spatial variability in rainfall has also observed during the past few decades across Asia. Similarly, water shortages in Pakistan, India, Nepal and Bangladesh have attributed to issues such as rapid urbanization and industrialization, population growth and inefficient water use that are aggravated by changing climate and its adverse impacts on demand supply and water quality. The key vulnerability of Pakistan Water Resources to Climate Change is increased variability in river flows due to change in frequency and intensity of extreme Climate events, the glacier retreat, increased Glacier Lake Outburst Floods (GLOFs), river floods and droughts, depletion of water storage capacity, due to siltation/sedimentation, flash flooding, water-logging and salinity, degradation of environment causing impacts on water quality, shrinking wetlands and increasing demands for water in all the sectors. 5

22 4.1 Deglaciation The 20th century has witnessed glacial fluctuations on a global scale. This has been a period of dramatic glacier retreat in almost all alpine regions of the globe, with accelerated glacier and icefields melt in the last two decades. The phenomenon of glacier retreat is of particular concern to Pakistan since its economy depends heavily upon agriculture, which in turn depends upon the melt water from the glaciers and snowmelt in HKH region. It is particularly worrisome in the light of following reports forecasting that Himalayan glaciers are retreating at a faster rate in contrast to the glaciers from other mountain regions affecting the flows of rivers of the Indus Basin Worldwide Glaciers Retreat The glacier cover of mountain regions worldwide has decreased significantly in recent years as a result of warming trends. A recent comparison of historical glacier data with images from the ASTER (Advance Space Borne Thermal Emission and Reflection Radiometer) instrument on NASA s TERRA Satellite by the United States Geological Survey revealed a significant shrinkage of mountain glaciers in the Andes, the Himalayas, the Alps and the Pyrenees over the past decade (Wessels et al. 2001). These observations are consistent with published results from many other glacier studies around the world that also recorded rapid glacier retreat in recent years. A study by Dyurgerov and Meier (1997), who considered the mass balance changes of over 200 mountain glaciers globally, concluded that the reduction in global glacier area amounted to between 6,000 and 8,000 km 2 over a 30 year period between 1961 and According to Haeberli and Hoelzle (2001) of the World Glacier Monitoring Service (WGMS), the measurements taken over the last century clearly reveal a general shrinkage of mountain glaciers on a global scale. They reported that the trend was most pronounced during the first half of the 20th century, that the glaciers had started to grow again after about 1950 but the glacier retreat has been accelerating again since the 1980s at a rate beyond the range of pre-industrial variability. Based on various scientific investigations IPCC (1996) in its Second Assessment Report forecasts that up to a quarter of the global mountain glacier mass could disappear by 2050 and up to half could be lost by 2100 (Rees and Collins, 2004) Himalayan Glaciers Retreat Several studies have reported Himalayan glaciers to be receding like other glaciers in the world (Mayeswki and Jeschke, 1979; Naithani, et al., 2001) with rate of the recession varying with region and terrain characteristics. According to the assessment made by Shrestha (Shrestha, 2006) based on various studies, 67% of glaciers were found retreating at a starling rate in the Himalayas and the major causal factor was identified as climate change. A remarkably rapid recession has been reported in the case of 30 kilometer long Gangotri glacier in the Eastern Himalayas. It is reported to have retreated by about 2 km over the last 200 years, of which about 850 meters has been in recent 20 years (Naithani et. al. 2001). The rate of recession of its snout (the point at which the glacier ends), which corresponded to 18 m per year between 1935 and 1990, is now reported to have increased to more than two and a half times this value per year (WWF Nepal, 2005; Hasnain 2006). 6

23 Studies have shown that between 1970 and 1989, most glaciers in the Everest region of the Himalaya had retreated 30-60m. To the west, in the Dhaulagiri region, field studies carried out before 1994 showed similar trend. Nepal s most studied glacier in Tsoronghimal underwent a 10 m retreat between 1978 and A number of other glaciers studied in Nepal and India were also found receding at an increasing rate (Shrestha, 2006). According to Rees & Collins (2004) the Working Group on Himalayan Glaciology (WGHG) of the International Commission for Snow and Ice (ICSI) reported in 1999 that: Glaciers in the Himalayas are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 is very high. Although the glaciers in the HKH region are generally reported to be diminishing, there are some contrary findings as well. For example, (Hewitt, 2005) has reported widespread expansion of larger glaciers in the Central Karakoram, accompanied by an exceptional number of glacier surges. According to him there is a continuing risk in the Karakoram Mountains from glacial outburst floods generated by surging tributary glaciers blocking main un-glaciated valleys; such an event has caused extreme floods in the past (Archer, 2002). 4.2 Impacts of Deglaciation Worldwide According to the IPCC AR4 by mid-century, annual average river runoff and water availability are projected to increase by 10-40% at high latitudes and in some wet tropical areas, and decrease by 10-30% over some dry regions at mid-latitudes and in the dry tropics, some of which are presently water stressed areas. Also there is an emerging evidence of present crustal uplift in Alaska due to recent melting of glaciers. IPCC (2001) has pointed out that glaciers and ice caps are one of the key indicators of ongoing climatic change. Glaciers and ice caps are components of the Earth s Cryosphere and the continual wasting of these ice bodies contributes to global sea level rise. Melt water production from glaciers at higher rate can lead to an increase in the occurrence of natural hazards in glacier-fed basins. Knowledge of the changes in the balance of glacier ice is thus of prime importance in modeling the interactive processes between climate and the Earth s global dynamic systems, and in the prediction of water availability in more specific regions of the Earth s surface Himalayan Region Glacier melt in the Himalayas is projected to increase flooding, rock avalanches from destabilized slopes, and affect water resources within next two to three decades. This will be followed by decreased river flows as the glaciers recede (IPCC, 2007). 7

24 According to the World Bank Report, 2005, Pakistan s Water Economy: Running Dry Western Himalayan glaciers will retreat for next 50 years causing increase in Indus River flows. Then the glacier reservoirs will be empty, resulting in terrifying decrease of 30% to 40% in flow of Indus River over the century. A three-year modeling study conducted recently by Centre for Ecology and Hydrology, Wallingford, UK and Alpine Glacier Project, University of Salford, UK reports that in the Upper Indus the mean river flow will increase between +14% and +90% (compared to the baseline) over the just few decades and these will generally be followed by flow decreasing to between -30% and -90% of baseline by the last decade of the studies time horizon (Rees & Collins, 2004). 4.3 Increased Variability in River Flows The flows of the Indus and its tributaries vary widely from year to year and within the year. As shown in Figure 3, the annual flow of Indus, measured at Kalabagh, varied between 120 MAF and 63 MAF during the period As is the case with the water availability, there is significant variation in annual flows to the sea (Fig.4). For example, in the flood years and , 81 and 92 MAF water went to the sea whereas in the drought years , and flows to the sea were in the range of 1-3 MAF Indus at Kalabagh Annual Inflows ( ) Annual Inflows (MAF) Years Data Source: Indus River System Authority (IRSA) Figure 3: Annual Flow Variations of the Indus River at Kalabagh 8

25 Figure 4: Escapage to Sea Down Below Kotri ( ) Data Source: Technical Committee on Water Resources, Government of Pakistan, May 2005 Deglaciation in Karakoram Himalayas is, of course, not the only way in which climate change is likely to affect the availability and timing of run off; both of these could also be affected through markedly variable rainfall in magnitude, time of occurrence and its aerial distribution. Almost twothirds of the rainfall is concentrated in the three summer months of July - September. The mean annual rainfall in Pakistan varies from less than 100 mm in Balochistan and parts of Sindh provinces to over 1500 mm in the foothills of northern mountains. 5. Analysis of IRS Flows in context of Glaciers Recession and Temperature Increase 5.1 Trend of Historical Flows The historical annual river flows data for Indus, Jhelum, Chenab and Kabul acquired from IRSA have been analyzed to check if these show any systematic linear trend over the period for which the data were available. The results are shown in Figures 5(a-d). There is no significant change in average flow of Indus measured at Kalabagh (Fig.5a) and at Tarbela (Fig.5b). Similarly there is no significant change in the average flow of Jhelum measured at Mangla (Fig.5c). Although there is an increasing trend in the flow of Chenab measured at Marala (Fig.5d), there is also a significant decreasing trend in the flow of Kabul measured at Nowshera (Fig.5e). We therefore conclude that so far, there is a little evidence that the average annual flow of IRS Rivers have been affected by glacier melt due to climate change. However, to see the likely effects of glaciers recession and temperature increase on Indus River flows, a hypothetical scenario is generated by using UBC Watershed Model. 9

26 Figure 5a: Trend in Annual Inflows of Indus at Kalabagh ( ) Data Source: Indus River System Authority (IRSA) Figure 5b: Trend in Annual inflows of Indus at Tarbela ( ) Data Source: Indus River System Authority (IRSA) 10

27 Figure 5c: Trend in Annual Inflows of Jhelum at Mangla. Data Source: Indus River System Authority (IRSA) Figure 5d: Trend in Annual Inflows of Chenab at Marala ( ) Data Source: Indus River System Authority (IRSA) 11

28 Figure 5e: Trend in Annual Inflows of Kabul at Nowshera ( ) Data Source: Indus River System Authority (IRSA) 5.2 Projected Flows of Indus River using UBC Watershed Model Hydrological models provide a mean of systematically studying the impacts of change in climatic conditions, glacier melt, change in land cover etc. on river flows. A few scientists have used such models to study the impacts of deglaciation on water resources in Himalayan Rivers (Rees and Collins, 2004, Shreshta, 2006) and produced river flows under different projected climate change scenarios. In line with these studies, the impact of deglaciation on the flow of Indus River at Besham Qila (just above Tarbela reservoir) is studied by GCISC using UBC (University of British Columbia) Watershed Model. The model was calibrated and validated using historical climate and river flow data covering the time span It was then applied to work out the overall river flow as well as the contributions to the flows arising from glacier melt, snow melt and rain for a hypothetical scenario in which the temperature was assumed to have been increased uniformly by +3 0 C throughout the year while the glacier area was assumed to have been reduced by 50%. In Figure 6 we compare the results for the overall flows and the glacier contribution in the hypothetical scenario with the corresponding base year values. It may be noted that glacier melt will start contributing early in the season and more water will be available during the spring but the summer flows will considerably decrease. On annual basis the flow is reduced by 15%. Efforts are now underway to generate flow patterns over the next several decades using the temperature and precipitation scenarios worked out by the GCISC Climatology Section inline with the IPCC SRES scenarios. 12

29 Mean Monthly Flows for the Period of Record Discharge (Cumecs) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Base Runoff Base Glacier melt CCS Runoff CCS Glacier melt Figure 6: Mean Monthly Flows for the Period of Record Main Results: 1. Annual flows reduced by 15% 2. Intra-annual flow pattern changed considerably 6. Adverse Impacts and Adaptation Measures 6.1 Major Concerns Briefly speaking, the major concerns for Pakistan due to extreme climatic events and melting of glaciers under global warming conditions are: Deglaciation in Karakoram Mountains at increased rate may provide relatively more water in the first few decades but the flows would decrease thereafter due to reduced glacier mass and will come down to their previous level depending upon the precipitation input. Increased frequency and intensity of floods and droughts due to reduction of natural reservoirs and variations in precipitation input. Due to change in frequency and intensity of precipitation events, inter-annual pattern of flows in the Indus Basin Rivers may change considerably. Inadequate & non-regulated escapage of flows below Kotri and sea level rise may cause further sea water intrusion in the delta of Indus and other coastal areas of Pakistan. 13

30 Increased floods resulting from glacial lakes outbursts (GLOF) in Western Himalayas are foreseen. Increased sedimentation due to high intensity rains and loss of reservoirs capacity. Some of these concerns are discussed below and the corresponding adaptation measures are identified. 6.2 Floods Floods are one of the major natural calamities in Pakistan. These are mainly caused by heavy concentrated rainfall over the upper catchments of the main rivers. In the foothills of glacial mountains floods are also caused by outburst of glacial lakes. Pakistan has a unique flood related problem in the sense that the greater part of the flood generating upper catchments of the rivers lie across the border in India/Indian-held Kashmir. This situation calls for obtaining the river flow data for some specific sites from India. This is provided by an agreement between Pakistan and India through their respective Commissioners for Indus Water which is renewed annually. Monsoon currents originating in the Bay of Bengal and resultant depressions often cause heavy downpour in the Himalayan foothills. These are additionally affected by weather systems from the Arabian Sea (by seasonal lows) and from the Mediterranean Sea (through westerly waves) which occasionally produce destructive floods in one or more of the main rivers of the Indus River System. Analysis of past 50 years flood data for Pakistan taken from EM-DAT website shows that the number of events per decade has considerably increased during the last two decades, which incidentally is the period during which the average global temperatures have been the highest since the mid eighteenth century (Fig.7). Pakistan, being the downstream user of the rivers and also embroiled in political conflicts with the upper riparian state India, has to be particularly careful about flood management. India has several structures in place that augment its capability to transfer flood surges to Pakistan this has happened in the past. India constructed the Bhakra Nagal Dam on Sutlej, the Pong Dam on the Beas and the Thein Dam on the Ravi. 14

31 Figure 7: Decadal Flood Frequency in Pakistan ( ) Data Source: The year wise analysis of past data on floods in Pakistan from 1950 to 2006 shows decreasing trend from 1950 to 1972 and then rapid increase thereafter (Fig.8). Figure 8: Number of floods recorded in each year ( ) with a quadratic trend 15

32 During the last 60 years, Pakistan has suffered a cumulative financial loss of more than Rs.385 billion and the loss of more than 7,800 people as a result of 16 major floods events (FFC Annual Report, 2007). Heaviest direct flood damages in Pakistan occur to infrastructure, agricultural crops, damage to urban and rural property and public utilities as well. Now there is a growing consensus that the impacts of climate change may well lead to an increase in both the frequency and magnitude of floods. This requires careful policy planning and formulation of strategies to combat and minimize the destruction which they cause. As an adaptive measure increased water storage capacity will be required to store water during the high flood periods so that the same could be used during low flow periods of the same year but also in subsequent years if they happened to be drought years. Currently, Pakistan has very little storage capacity i.e. only 150 cubic meters per capita as compared to 2200, 5000 and 6000 cubic meter per capita in China, Australia and United States respectively (World Bank Report, Pakistan s Water Economy: Running Dry, 2006). The reservoir capacity in Pakistan is also very low in relation to average (for the period ) annual flows in IRS 142 MAF, it corresponds to only 9% of such flows, as compared to 30% of the average annual rivers flow in the neighboring country, India (State Bank of Pakistan, ). 6.3 Glacial Lake Outburst Flood (GLOF) Glaciers movement is the major cause of abrading bedrock and valley sites. Advancing glaciers take lot of debris with them and spread near the snouts. They leave all their debris on retreat forming lakes surrounded by the moraines banks. Such lakes start filling with the melting ice as long as the moraine walls can hold the water pressure. With rapid melting of glaciers, glacier lakes level can rise over the banks formed of moraines can give way, leading to the catastrophic events known as Glacier Lake Outburst Flood (GLOF), thus making these high altitude lakes potentially very hazardous. Most of such dangerous glacial lakes are concentrated near the headwaters of rivers basin just downstream of glaciers. Sometimes high floods have been caused by the formation of temporary natural lakes by landslides or glacier movement and their subsequent collapse. In Pakistan, 2420 glacial lakes are identified in the HKH region covering a total area of almost 126 Sq. Km. Among these identified glacial lakes 52 are declared as potentially dangerous glacial lakes (Roohi et al,. 2005). These potentially dangerous lakes can burst anytime and cause flash floods and are continuous risk to the downstream livelihood as well as hydro-power generation plants. There does not appear any specific coping mechanism against GLOF except the development of an effective monitoring and early warning system to forewarn the downstream dwellers of any imminent dangers of GLOFs. Such kind of adaptive measures to prevent GLOFs are very important to take place in Northern Areas because WAPDA has most of its future hydropower projects in these areas. 16

33 6.4 Droughts When there is marked depletion of surface water causing very low stream flow and drying of lakes, reservoirs and rivers, it is called a hydrological drought. This occurs on the local, regional or subcontinental scale which spreads in horizontal direction. In this spatial distribution, drought can last from a few weeks during a season with intermediate breaks of spells of good rains, to several years in succession. Droughts are due to the low precipitation over a specified period and when their duration prolongs, evapo-transpiration plays vital role in reducing the surface water and soil moisture. Concurrently, groundwater and river discharges slow down. The situation is aggravated if flow intervention takes place in the upstream parts of the rivers. Virtually droughts may appear in all climates. The concise definition of the droughts is dependent on its geographical location and often calculated by comparing the recent precipitation of the site to the average. Semi-Arid areas having less than 500mm of annual rainfall host droughts as permanent climatic condition. Droughts also occur even in high rainfall condition if its temporal and spatial distribution does not fulfill the moister demands of the crop. For example, in South Asia many rivers, lakes and underground aquifers are fed by monsoon precipitation which follows nonuniform spatial and temporal distribution pattern over the region. Although the severe droughts in South Asia mostly occur in the pre-monsoon periods and post-monsoon period, the pre-monsoon droughts occasionally extend throughout the monsoon period due to late onset of monsoon and weak monsoon activities (S. Nandargi et. al., 2006). Pakistan is an arid country receiving low rainfall and higher solar radiation over most parts of the country. Total land area of Pakistan is 88 million hectares. About 59 per cent of the total area is classified as rangelands. Most of this area receives less than 200mm rainfall annually. Pakistan experienced the serious drought situations from facing adverse freshwater dearth. Droughts severely affected the parts within and outside Indus Basin making the provinces of Punjab, Sindh and Balochistan most vulnerable. Out of sixteen districts in the Sindh Province, eight were affected by drought during the period with four districts being severely affected. Again, as in the case of floods, the frequency and intensity of droughts are expected to increase with increase in global warming. In order to cope with this situation a two pronged approach is required. Firstly, as discussed earlier in the context of floods, the reservoir capacity needs to be augmented considerably in order to store water during high flow/flood periods and use this water during the drought periods within the same year or in subsequent drought year. Equally important for an arid country like Pakistan, is to reduce its water losses though seepages from canals and water channels etc. and to use the limited available water in a highly efficient manner. These aspects are discussed by our colleagues from Agriculture Section (Iqbal et. al., 2007). 6.5 Sea Water Intrusion According to IPCC Fourth Assessment Report, 2007, the greatest increase in vulnerability is expected to lie on the coastal strips of South and South East Asia. In Pakistan there is 1050 km long coastline spread along the provinces of Sindh and Balochistan. In Sindh province mangroves are found in the Indus Delta and have an area of about 600,000 ha. In Balochistan province, the mangroves total area is estimated to be 7,340 ha. These mangroves provide food and shelter 17

34 during larval stage of the life cycle for some 80% of the commercial species caught from water. Indus Delta encompasses 17 major creeks, many minor creeks and mudflats. Indus delta mangroves are the largest arid climate mangroves in the world. Sindh Forest Department has under its control an area of 345,000 ha of the Indus Delta as a protected forest. However, recent studies show that the area has shrunk to 160,000 from 205,000 hectares ( The survival of these mangroves is highly dependant on perpetual freshwater from the River Indus. Currently, the Indus Delta faces major threats due to inadequate fresh water flows. Another major threat is the sea level rise, which could significantly contribute to losses of coastal wetlands and mangroves. Besides mangroves destruction, other natural resources degradation is also evident everywhere downstream Kotri Barrage especially in the Deltaic Region where million of acres of land submerged in water due to the less water in Indus Delta and sea water intrusion. In rivers with a long duration of high flows, fresh water prevents saline water of the sea from intruding into the creeks and channels of the Delta by pushing it away from the river s mouth. But due to the low flows of freshwater downstream Kotri the seawater intrudes, finding no resistance, deteriorating the agriculture belts and coastal wetlands. This seawater intrusion is also caused by sea level rise, a worldwide Climate Change related phenomenon. The IPCC Working Group II (2001) Third Assessment Report identifies sea level rise as one of the most important coastal impacts of global warming, and identifies several key impacts. Changes in sea level are nonuniform spatially. According to Institute of Oceanography, Pakistan, the sea level at Pakistan s coastline shows an increasing trend of 1.1 mm/year, i.e. within global average range of 1.7±0.5 mm/year for the 20 th Century (IPCC, 2007). In the 1991 water accord agreed by the Provinces of Pakistan, almost 10 MAF of water is considered as good enough for Downstream Kotri. But the graph of annual escapage to the sea shows that the required 10 MAF water was not available in low flow years from 1999 to 2003 (Fig.4). The Indus delta also runs dry for several months in the Rabi season (October March) each year. The surplus water is available only between days during the flood season (June- September). According to WAPDA (Water and Power Development Authority, Pakistan) 35 MAF on average water is out flowing to sea each year. Therefore, it is a very precarious situation that in spite of these being, on the average, an excess supply of almost 25 MAF, it is not being put to use to regulate flows down stream Kotri simply because of inadequate storage capacity in the country. Therefore, there is a pressing need for building additional reservoirs for 25 MAF per year of surplus water going to the sea which could be partly used to regulate the release of 10 MAF/year of water downstream Kotri. 6.6 Sedimentation and Loss of Reservoir Capacity Glaciers and snow melting are associated with the soil erosion and sediment transport. This erosion is rapid in the areas where the ice flows at high velocity. Sediments are eroded and join glaciers by several processes. Once the glaciers incorporate these sediments, they may carry these sediments downstream and release in the ablation zone. Pakistan, situated in arid and semi-arid zone, is suffering the soil erosion problems seriously. This erosion, caused by glacier/ice melt and decrease in natural vegetation due to deforestation and improper land usage, deposits heavy sediments in the dams and reservoirs downstream. 18

35 Indus river catchment above Tarbela reservoir is particularly subject to heavy weathering effect under severe climatic conditions and due to the melting of glaciers. These glacier melts also produce sediments in large quantity each year. Indus river overall carries about 0.35 MAF (0.435 BCM) of sediment load annually, almost 60% (0.2 MAF) of which deposits in the reservoirs, canals, and irrigation fields (Kahlown, 2002). Reservoirs have to face indispensable and unavoidable loss due to sedimentation that significantly reduces their storage capacity. In spite of an already short capacity of only MAF (Table 2), Pakistan loosing existing capacity day by day due to the heavy deposits of sediments in the reservoirs. Figure 9 shows the reduction of storage capacity of three major reservoirs of Pakistan namely, Tarbela, Mangla and Chashma. The Indus river brings 200 million tones (MT) of sediment to Tarbela reservoir while Jhelum River brings abut 59 MT to Mangla reservoir. The gross capacity of Tarbela and Mangla is reducing annually at rate of about 110,000 Acre-Feet and 60,000 Acre-Feet respectively (GoP, Planning Commission, 2005). Table 2: Live Storage Capacity of Pakistan as of 2003 Dam (Year) River Live Storage (MAF) Tarbela (1976) Indus 9.69 Mangla (1966) Jhelum 5.34 Chashma (1971) Indus 0.61 Warsak (1960) Kabul 0.04 Baran (1962) Kurram 0.09 Hub (1983) Hub 0.76 Khanpur (1984) Haro 0.09 Tanda (1965) Kohat Toi 0.06 Rawal (1962) Kurang 0.04 Simli (1972) Soan 0.02 BKD Khan (1900) Pishin 0.04 Hamal Lake 0.08 Manchar Lake Indus 0.75 Kinjhar Lake Indus 0.32 Chotiari Lake Indus Total Storage Source: Pakistan Development Forum, Presentation on Planning for Water Resources, by Dr. Shahid Amjad Chaudhry, Deputy Chairman, Planning Commission, Government of Pakistan, May

36 Figure 9: Loss of Storage Capacity of Three Major Reservoirs and Total Data Source: Pakistan Development Forum, Presentation on Planning for Water Resources, by Dr. Shahid Amjad Chaudhry, Deputy Chairman, Planning Commission, Government of Pakistan, May 2003 The rate of loss of reservoir capacity may possibly increase in future as a result of increased glacier melting due to climate change. This risk can be mitigated by adopting appropriate preservation methods delaying the process of silting up of the reservoirs to some extent. The most economical method is construction of a series of dams on the river to trap the sediment in upstream reservoirs and store almost sediment free water in the lower reservoirs (like the proposed Kalabagh Dam downstream to Tarbela). To slow down the storage loss process of above reservoirs, an extensive watershed management program has been undertaken by WAPDA in the catchments of Mangla and Tarbela Dams, which encompasses forestation and sediment traps construction to reduce the silt deposition in these reservoirs. The project of Mangla Dam raising is expected to be completed by the end of 2007; it will add up to 2.9 MAF to the current live storage of Mangla Dam (Website of the Parliamentary Committee on Water Resources website, There are also some other proposed/under construction dams that will improve the storage capacity of the country. 6.7 Shrinking Wetlands There is a broad and growing consensus that wetlands are critically important ecosystems that provide globally significant social, economic and environmental benefits. In Pakistan 19 sites are declared as of international importance covering an area of almost 1,343,627 hectares (Ramsar Convention on Wetlands) and are under threat due to the projected changes in climate. Predictions of a warmer climate and changes in precipitation patterns would strongly affect wetland ecological functions through changes in hydrology, biogeochemistry, and biomass accumulation. According to the IPCC Fourth Assessment Report, Species ranges are likely to shrink by About one fifth to one third of the species may be committed to extinction by that time with those risks increasing for the second half of the century. 20

37 Pakistan had produced a Wetlands Action Plan in 2000, the lack of a comprehensive Wetlands Management Strategy hindered policy formation, coordination and management of wetlands at a national scale. Additionally, options for financial sustainability had not been fully explored to enable the proliferation of long-term initiatives in biodiversity conservation. As a result, such initiatives tended to be donor-driven and short-lived. To tackle this issue effectively a comprehensive sustainable wetland management plan needs to be developed. 6.8 Groundwater Depletion After the surface water the groundwater is the major source of freshwater in Pakistan. The vast aquifer of freshwater underlying the Indus Plains, mainly recharge by the precipitation, the river flows, and the seepage from the canal systems, distributaries, watercourses and application losses in the irrigated fields. The total potential recharge in the useable groundwater areas in the Canal Commands and the riverine areas is estimated as 66.8 MAF (Kahlown, 2004). Groundwater in the Indus Basin aquifer, which can be withdrawn to put to beneficial use is neither unlimited nor permanent and has to be recharged. A larger yield can be obtained temporarily by pumping in excess of the prevailing recharge but can result further in a decline of water table and serious problems like quality and quantity of groundwater. This aquifer with a potential of about 50 MAF is being exploited to an extent of about 40 MAF by over 562,000 private and about 16,000 public tube wells (Kahlown, 2004). According to IPCC Technical Paper on Climate Change and Water Groundwater levels of many aquifers around the world show a decreasing trend during the last few decades, but this is due to excessive groundwater pumping and not to climate-related decrease in groundwater recharge. To address the issue of depleting groundwater, various methods are in practice to recharge it. The most widely used method is delay action dams, percolation basins, modified streambeds, diversion structures, ditches, furrows, and recharge through injection wells, however, application of these methods is subject to the local condition and topographic characteristics. 6.9 Water Logging and Salinity Several areas of Pakistan in particular, Punjab and Sindh suffer from water logging and salinity because of poor drainage system in the country. Salts carried in surface water and mobilized through unregulated ground water pumping accumulate in the root zoon, adversely affecting crops and agriculture productivity. According to the Drainage Master Plan (DMP), 39% of gross commanded area in the country is water logged and is affected by salinity. Twelve percent has a water table depth up to 150 cm (5 ft) while other 27% of surface soil is saline (4% moderately saline, 7% severally and 6% sodic). The experts are of the opinion that due to salinity problem 25% agriculture productivity is reduced in Punjab only. This salinity problem may be increased due to increased evaporation under higher projected temperature and needs to be addressed by adapting appropriate measures. 21