Home Essay/Articles ARTICLE : IMPACT OF CLIMATE CHANGE ON WATER RESOURCES
ARTICLE : IMPACT OF CLIMATE CHANGE ON WATER RESOURCES
Saturday, 07 February 2015 05:11


 

IMPACT OF CLIMATE CHANGE ON WATER RESOURCES

In order to minimize the adverse impacts of climate change on water resources and attaining its sustainable development and management, there is a need for developing rational adaptation strategies. 

IN INDIA the distribution of rainfall is highly non-uniform both in terms of time and space. As a result water is required to be stored and utilized for meeting the demands of different sectors throughout the year. Efficient water management requires sustainable development of the available surface and ground water resources and their optimal utilizations.


Although specific regional effects in this regard are still uncertain, climate change is expected to lead to an intensification of the global hydrological cycle  and can have major impacts on regional water resources, affecting both ground and surface water supply. In its Fourth Assessment Report, the IPCC suggests that average temperatures will climb 1.56 to 5.44°C in south Asia by 2099. Dry season rainfall will drop by 6 to 16 per cent, while wet season rains will increase by 10 to 31 per cent. Such shifts in temperature and precipitation patterns could carry major repercussions for India\'s freshwater resources and food production. Rising surface temperatures appear to be contributing to melting of snow and ice pack in the Himalaya, thus threatening the water supplies on which hundreds of millions of people depend. As per IPCC analysis India could suffer from outright water stress – annual availability of less than 1,000 cubic meters per capita – by 2025, and gross water availability could fall as much as 37 percent by mid-century. In addition to the implications for drinking water and sanitation, this could considerably diminish crop yields in the region. Temperature increase of as little as 0.5 to 1.5°C might trim yield potentials for Indian wheat and maize by 2 to 5 per cent. For greater warming, above 2.5 degrees centigrade, the losses in non-irrigated wheat and rice yields in south Asia could cut net farm level revenues by 9 to 25 per cent.


Even under the most conservative climate change scenarios, net cereal production for south Asian countries is expected to tumble by at least 4 to 10 per cent.


Where some parts of India will face shrinking water supplies, others will face rising seas. Average global sea levels are projected to rise at a rate of 2 to 3 mm per year over the coming 100 years. Low end scenarios estimate sea levels in Asia will be, a minimum, 40 cm higher by the end of the 21st century. The IPCC calculates that this would expose from 13 million to 94 million people to flooding, with about 60 per cent of this total in South Asia. In India, sea level rise of 100 cm would inundate 5,763 km3 of the country\'s landmass. Because of their high population density, susceptibility to coastal flooding and saltwater intrusion from sea level rise, and exposure to storm surges, the IPCC has specifically designated several of India\'s low-lying coastal river deltas-the Ganges (shared with Bangladesh), the Godavari, the Krishna, and the Mahanadi- as particular "hotspots" of climate change vulnerability.


Utilizable Water Resources Potential of India

Surface Water

The utilizable water potential of the country has been variously estimated in the past. The Central Water Commission estimated the utilizable surface water in each river basin considering the suitable sites/locations of diversion and storage, as 690 BCM. The National Commission for Integrated Water Resources Development Plan (NCIWARDP 1999) as well as the Standing Sub-Committee for \'Assessment of Availability and Requirement of Water for Diverse Uses in the Country\' constituted by the Ministry of Water Resources (August, 2000) have adopted this value.


Ground Water

The annual replenishable ground water resource for the country was estimated at 433 billion cubic maters (bcm) as on March 2004. The sources of replenishment include rainfall (67%) and other sources like canal seepage, return flow from irrigation , seepage from water bodies and artificial recharge due to water conservation structures (33%)


Static Ground Water Resource

An assessment of the quantum of static water resource available in the country has been carried out by CGWB on the basis of the depth of availability of ground water and the productivity of deeper aquifers. The total estimated static ground water resource is 10,812 BCM.


Per Capita Availability

The average annual per capita availability of water taking into consideration to population of the country as per the 2001 census, and the population for the year 2025 and 2050 is as under:

Year

Population (in Million

Per capita availability (in Cubic Meter)

2001

2025

2050

1027 (2001 census)

1394 (projected)

1640 (projected)

1820

1340

1140


Eight river basins viz. Cauvery, Pennar,  Mahi, Sabermati, Tapi east flowing rivers between Mahanadi and Pennar, east Flowing Rivers between Pennar and Kanyakumari and West Flowing rivers of Kutch and Saurashtra, including Luni are already water scarce. i.e. having per capita water availability less than 1000m3 per year. By 2025 three more river basins viz. Ganga, Krishna and Subarnarekha may add to the list of water scarce basins taking the total water scarce basins to eleven by 2025. By 2025 Indus basin may also become water scarce while Godaveri basin may be close to water scarce level.


Presently, the total live storage capacity of the dams completed in the country has gone up to 225 BCM. Besides, dams under construction will create an additional live storage capacity of 64 BCM and Dams which are under formulation/consideration will create around 108 BCM additional live storage. Taking the population as 1027 million as per 2001 census, the per capita storage in the country is about 219 m3.


Climate Change: Assessment Studies and Major Threats

With respect to the global climate change scenarios, impact on water resources has been summarized as below:


• With unmitigated emissions, by the 2080s, large changes are predicted in the availability of water from rivers, with substantial decreases in Australia, India, Southern Africa, most of South America and Europe, and the Middle East and increases across North America, central Asia and central eastern Africa

• An emissions scenario where CO2 stabilizes at 750 ppm slows down the rate of change in river flows by about 100 years (more in Aisa, slightly less in Europe). Stabilization 550 ppm delays the change still further, particularly in South America and Asia.


Any climate change impact assessment on water resources study requires the down-scaling of the precipitation and other variables such as temperature, relative humidity, solar radiation, wind direction and wind speed from the global scale to the regional scale. The future predictions are described in term of SRES (Special Report on Emissions Scenarios) storyline scenarios (IPCC, 2007) which are labeled AI, A2, B1 and B2, describing the relationships between the forces driving greenhouse gas and aerosol emissions and their evolution during the 21st century. Each scenario has made assumptions that are dependent on demographic, social, economic, technological, and environmental developments.


The predications made on the future scenarios through the regional level downscaling are used by researchers to quantify the impacts on water resources. At the national level the NATCOM (NATional COMmunication to the United Nations Framework Convention on Climate Change, 2004) project has been the first one in this direction.


The latest high resolution climate change scenarios and projections based on Regional Climate Modeling (RCM) system applied IPCC scenarios A2 And B2 to show the following:


• 3 -5 degrees annual rise in mean surface temperature by the end of century, under A2 scenario and 2.5 to 4° C under B2 scenario, with warming more pronounced in the northern part of India.


• A 20% rise in all India summer monsoon rainfall over all states, except Punjab, Rajasthan and Tamil Nadu, which show a slight decrease.

• Increase in extremes in maximum and minimum temperatures and precipitation, particularly over the western coast and west central India.

However, studies by the Central Water Commission (Thatte, 2000) and , Gupta and Deshpande, 2004 have predicted that per capita availability of water will go down drastically by 2050, even without considering climate change, due to population growth.


A case study by Roy et al (2003) on the impact assessment of climate change on river water availability in the Damoder basin concludes that decreased peak flows would hinder natural flushing of stream channels leading to loss of carrying capacity and decreased production of non-monsoonal crops.

A comprehensive study carried out to quantify the climate change impact on majority of Indian river systems (Gosain et al, 2003) has concluded that although there is an increase in precipitation in some of the river systems for the Green House Gas scenario, the corresponding runoff for these basins has not necessarily increased due to increase in evapo-transpiration on account of corresponding increased temperatures. Two river systems which are predicted to be worst affected from floods are Mahanadi and Brahmani. Decrease in precipitation may be experienced in other river basins like Sabarmati and Mahi to the extent of two thirds of prevailing runoff. This may lead to severe drought conditions in future in these basins.


There has been widespread retreat of glaciers worldwide during the current century (IPCC, 2007). If current warming rates are maintained, Himalayan glacier could decay at very rapid rates, shrinking from the present spread of 500,000km2 to 100,000 km2 by the 2030s. Retreat of the Himalayan glaciers and its impact on the water availability are important issues which are debated from time to time. Indian Himalayas have nearly 9575 glaciers covering an area of about 38000 km2 (GSI, 2007)… Kulkarni et al. (2007) have studied glacial retreat of 466 glaciers in Chenab, Parbati and Baspa basins from 1962 using Remote Sensing technique. It is found that there is overall reduction in glacier area from 2077 km2 in 1962 to 1628 km2 at present, an overall deglaciation of 21%. Study of Geological Survey of India (GSI) has revealed that glaciers are receding at an alarming  rate viz. Gangotri (17.5m/yr), Dokriani (17.5m/yr), Milam (13.3 m/yr), Pindari (23.5 m/yr) and Zemu (13.2 m/yer). This would lead to increased summer flows in some river systems for a few decades, followed by a reduction in flow in case glacial retreat continued.


The National Institute of Hydrology has conducted sensitivity analysis on some of the Himalayan basins i.e. Sutlej, Spiti and Dokriani basins and found that under warmer climate, there was reduction in melting from the lower part of the basin owing to a reduction in snow covered area and shortening of the summer melting season and, in contrast, an increase in the melt from the glacierized part owing to larger melt and an extended ablation period. Thus, on the basin scale, reduction in melt from the lower part was counteracted by the increased melt form upper part of the basin, resulting in a decrease in the magnitude of change in annual melt runoff. The impact of climate change was found to be more prominent on seasonal rather than annual water availability.
Sea-level rise could raise a wide range of issues in coastal areas. The potential impacts  of one metre sea-level rise include inundation of 5,763 sq km and 2,339 sq km in India and in some big cities of Japan, respectively (TERI, 1996; Mimura and Yokoki, 2004).


India, China and Bangladesh are especially susceptible to increasing salinity of their groundwater as well as surface water resources, especially along the coast, due to increases in sea level as a direct impact of global warming (Han et al., 1999) For two small, flat coral islands off the coast of India, the thickness of the freshwater lens was computed to decrease from 25 m to 10 m and from 36 m to 28 m for a sea-level rise of only 0.1 m (Boba et al., 2000).


An analysis of satellite images of fourteen of the world\'s major deltas (Danube, Ganges-Brahmaputra, Indus, Mahanadi, Mangoky, McKenzie, Missisippi, Niger, Nile, Shatt el Arab, Volga, Huanhe, Yukon and Zambezi) indicated a total loss of 15,845 sq km of deltaic wetlands over the past 14 years (Coleman et al., 2005). Increasing shoreline retreat and risk of flooding of coastal cities in Thailand, India, Vietnam and the United States have been attributed to degradation of coastal ecosystems by human activities, illustrating a widespread trend. Large-scale conversions of coastal mangrove forests to shrimp aquaculture have occurred during the past three decades along the coastlines of Vietnam (Bing et al., 1997), Bangladesh and India (Zweig, 1998), Hong Kong (Tam and Wong, 2002) the Philippines (Spalding et al., 1997), Mexico (Contreras-Espinosa and Warner, 2004), Thailand (Furakawa and Baba, 2001) and Malaysia (Ong, 2001).


IPCC Projection

The IPPC Report – 2007 states that "the gross per capita water availability in India will decline from about 1820 m3 per year in  2001 to as low as about 1140 m3 per year in 2050. India will reach a state of water stress before 2025 a state mentions that "the availability falls below 1000 m3 per capita. The report also mentions that "the availability of fresh water in India is expected to drop from around 1900 m3 currently to 1000 m3 by 2025 in response to the combined effects of population growth and climate change. The report has also predicted more intense rain, more frequent flash floods, increase in drought-affected areas and  extreme precipitation events in other areas. Water volumes stored in glaciers and snow cover are very likely to decline, reducing summer and autumn flows in the Himalayan river systems in the long run. At lower latitudes, especially the seasonally dry tropics, crop yield potential is likely to decrease for even small global temperature increase.


National Action Plan on Climate Change

The National Action Plan on Climate Change (NAPCC) has laid down the principles and has identified the approach to be adopted to meet the challenges of impact of climate change. A National Water Mission finds place among the eight missions identified. Its objective is to ensure integrated water resources management helping to conserve water, minimize wastage and ensure more equitable distribution both across and within states. The Mission will take into account the provisions of National Water Policy and develop a framework to optimize water uses by increasing water use efficiency by 20% through regulatory mechanism and differential entitlements and pricing. It will seek to ensure that considerable share of water needs or urban areas are met through recycling of waste water, and ensuring that the water requirements of coastal cities with inadequate alternative sources of water are meant through adoption of new and appropriate technologies such as low temperature desalination technologies that allow for the use of ocean water. The National Water Policy would be revisited in consultation with variability in rainfall and river flows due to climate change.
The Mission will seek to develop new regulatory structures, combined with appropriate entitlements and pricing. It will seek to optimize the efficiency of existing irrigation systems, including rehabilitation of systems that have been run down and also expand irrigation, where feasible, with a special effort to increase storage capacity. Incentive structures will be designed to promote water neutral and water positive technologies, recharging of underground water sources and adoption of  large scale irrigation programmes which rely on sprinklers, drip irrigation and ridge and furrow irrigation.


The Way Forward

It is a paradox that India possesses an apparently vigorous planning mechanism with sufficient investment and yet remains under-prepared vis-a-vis climate change impacts. The failing monsoon of 2009, followed by the unprecedented rains of early October in the southern states of India, established once more that India must ready herself to address such anomalies more frequently than ever. Obviously, physical resources will remain inadequate to brace the country for the new challenge of climate change unless they are bolstered by necessary institutional arrangements and backed by a holistic vision. The way forward in this regard would need to take care of the following:

Promote Adaptation Strategies

In order to minimize the adverse impacts of climate change on country\'s water resources and attaining its sustainable development and management, there are needs of developing rational adaptation strategies. Thus, due consideration is required to be given to the effect of climate change while planning, designing and operation of the water resources projects. These would be reflected in proper assessment of water resources, developing suitable hydrological design practices and operational policies for water projects, putting in place effective flood and drought management strategies, developing water efficient irrigation practices, etc.


Necessary Policy Changes

Key among the necessary policy changes are :

(i) Regional and transboundary cooperation in water security -India must take the lead in consulting SAARC nations to foster information sharing and joint management of transboundary water resources and perhaps shape a common stance on international climate change negotiations;

(ii) increased accountability by the different actors; and

(iii) decentralization of decision making.

Bridge Gaps in Knowledge

The studies done on the impact of climate change on various aspects of water availability in India are as yet very few and far between. As knowledge is a prerequisite for managing adaptive strategies, we need to bridge our knowledge gaps in all areas that are relevant to better planning. These would include having better observational data and data access, work on detection and attribution of present-day hydrological changes, higher resolution climate models, with better land surface properties and interactions, analysis of demand and supply of water on a monthly basis, process oriented models for studying impact of climate change on snow, ice and frozen ground, climate change impacts on water quality, impact assessment on ground water, etc.

 

Last Updated on Saturday, 07 February 2015 05:15