Water Availability and Demand In India, Mechanics of Tillage and Traction | Mechanics of Tillage and Traction Notes- Agricultural Engg - Agricultural Engineering PDF Download

Introduction

India with 2.4% of the world’s total area has 16% of the world’s population; but has only 4% of the total available fresh water. While the total water resource availability in the country remains constant, the per capita availability of water has been steadily declining since 1951 due to population growth. The twin indicators of water scarcity are per capita availability and storage. In estimation, planning and use of water resources one need to know the availability and demand to proceed further. This lecture presents the estimates of water availability and demand in India from recent reports under the following units.

1.1 Water Availability in India

India receives a total precipitation of about 4000 Billion cubic metres (BCM). However, rainfall in India shows a very high degree of spatial and temporal variability. Nearly 3000 BCM of precipitation occurs during the monsoon months from June till September. The spatial variability is also very conspicuous as it varies between 100 mm in Western Rajasthan and 11000 mm at Cherrapunji in Meghalaya. There are 13 major river basins in the country having a catchment area exceeding 200 km2. The flows in rivers vary significantly. Available water resources have been assessed to be 1869 BCM. However in view of the physiographical and topographical features, the utilizable water is assessed as 1123 BCM comprising of 690 BCM of surface water and 433 BCM of replenishable groundwater. The water resource potential of the country has been assessed from time to time by different agencies. The different estimates are shown in Table 1.1. It may be seen that since 1954, the estimates have stabilized and are within the proximity of the currently accepted estimate of 1869 billion cubic metre (bcm) which includes replenishable groundwater which gets charged on annual basis.

TABLE 1.1 Estimates of Water Resources in India

The details of India’s Water Budget are furnished in table 1.2.

TABLE 1.2   India’s Water Budget (BCM), 2009

1.2 Utilizable Water Resources Potential

Within the limitations of physiographic conditions, socio-political environment, legal and constitutional constraints, and the technology available at hand, the utilizable water resources of the country have been assessed at 1123 bcm, of which 690 bcm is from surface water and 433 bcm from groundwater sources (CWC, 1993). Harnessing of 690 bcm of utilizable surface water is possible only if matching storages are built. Trans-basin transfer of water, if taken up to the full extent as proposed under the National Perspective Plan, would further increase the utilizable quantity by approximately 220 bcm. The irrigation potential of the country has been estimated to be 139.9 MH without inter-basin sharing of water and 175 MH with interbasin sharing. Ultimate Irrigation Potential of States of India is given in table 1.3

Table  1.3   Ultimate Irrigation Potential by State (Unit : '000 Hectares)

1.3 Per capita availability of water

While the total water resource availability in the country remains constant, the per capita availability of water has been steadily declining since 1951 due to population growth. The twin indicators of water scarcity are per capita availability and storage. A per capita availability of less than 1700 cubic metre (m³) is termed as a water-stressed condition while if per capita availability falls below 1000 m³, it is termed as a water scarcity condition. While on an average we may be nearing the water-stressed condition, on an individual river basin-wise situation, nine out of our 20 river basins with 200 million populations are already facing a water-scarcity condition. Even after constructing 4525 large and small dams, the per capita storage in the country is 213 m³ as against 6103 m³ in Russia, 4733 m³ in Australia, 1964 m³ in the United States (US), and 1111 m³ of China. It may touch 400 m³ in India only after the completion of all the ongoing and proposed dams. The Per Capita Availability of Water in India during 2010 is tabulated in Table 1.4.

Table 1.4 : Per Capita Availability of Water in India during 2010

1.4 Water for nature

The question of a trade-off between competing claims on water becomes most important in the context of ecological requirement. The National Water Policy (NWP) places ecology in the fourth place in the order of priorities for water use. Yet, there is a general agreement amongst all that any water diversion needs to take care of river ecosystem downstream. The problem is of quantifying the Environment Flow Releases (EFR), that is the flow required for maintaining ecosystems. Usable water will be reduced to that extent. During 2004–05, the Ministry of Environment and Forests (MoEF) appointed a committee headed by Member, Central Water Commission (CWC), to develop guidelines for determining the EFR. The committee submitted its report in 2005. Depending on what the final accepted recommendation is, the minimum flow required for maintaining the river regime and environment will be decided and considered in water resources development and management.

1.5 Population growth & demographic changes and their impact

India with 2.4% of the world’s total area has 16% of the world’s population; but has only 4% of the total available fresh water. The total population of the country in 1901 was 238.4 million. After independence, our country witnessed a spurt in population growing at a rate more than 20% per decade. In 1951, it was 361.1 million which increased to 439.2 million in 1961 and then on to 683.3 millions in 1981. The surge was unabated through 1990s. The population of 846.4 millions in 1991 attained 1028.7 million at the turn of the twenty first century i.e in 2001. It is being forecast that the population could be of the order of about 1210 millions by 2011 on the basis of about 17.64% growth rate for the 2001‐2011 decade. It is obvious that urban growth trend is progressive while rural growth is regressive as per the emerging results of the Census study. Relatively increased rate of urban population growth would require relatively higher allocation of water for domestic purposes. Further, the industrial growth also calls for more requirement of industrial water supply. Related challenge also comes in the form of pollution of water which needs to be addressed as part of urbanization issues.

Considering the high variability in the yield of the rivers both temporally and spatially, conservation of water resources becomes very important. As per available information, a total of about 225 of surface water storage have since been created. Further due emphasis has been laid on water conservation through rainwater harvesting and artificial recharge to the groundwater. However, the per capita storage of about 190 cubic metres in the country is miniscule compared to per capita storages in countries like USA, Australia, Brazil & China which are about 5961, 4717, 3388 and 2486 cubic meters respectively. Due emphasis has to be laid on conservation of water, recycling of water into utilizable water, introducing efficient methods and better management practices. This is more so to meet the increasing demand of water for various purposes in view of growing population, industrialization and urbanization.

1.6 Water requirement for various sectors

Water Requirement for Various Sectors estimated by Standing Sub- Committee of MoWR and NCIWRD are in table 1.5.

TABLE 1.5 Water Requirement for Various Sectors

1.6.1 IRRIGATION REQUIREMENT

Irrigation Use is the most critical parameter in water management. NCIWRD estimates that the share of irrigation demand out of the total will decline to 72% by 2025 and to 68% by 2050 as revealed in Table above. The population for 2012 has been projected to be of the order of 1.2 billion by Census study. Hoping that the present decadal growth rate will decline steadily, a population of 1.58 billion, the upper limit adopted by NCIWRD will itself be under‐estimation for 2050. Therefore, for analysis, only the higher limit is adopted. Between 2025 and 2050, there is a projected demand gap of nearly 200 BCM. Considering from XII Plan onwards, the demand gap could be of the order of 250 BCM. Even if a fair percentage of this additional demand is borne by groundwater, the extra burden on surface irrigation will be of the order of 150 BCM to achieve self‐sufficiency by 2050. The need and urgency about creating more storage through Major & Medium Irrigation sector in the country is apparent.

1.6.2 NON‐IRRIGATION (DOMESTIC, INDUSTRIAL & ENERGY) REQUIREMENTS

Due to rapid industrialization and urbanization in a developing country like ours, the demands on domestic, industrial and energy requirements are expected to mount at a rapid rate. NCIWRD has projected for domestic‐industrial‐energy requirements, an additional demand of 100 BCM for 2050 over that of 2025. Considering from XII Plan onwards, it can be estimated to be of the order of 150 BCM. The extent of this additional demand can be realized from the fact that it is almost equal to the additional live storage capacity envisaged from projects likely to be commissioned in future.

1.7 Impact of climate change

With all these challenges notwithstanding, another challenge has emerged ‐ the global threat of climate change. It is understood in common terminology as 'Global Warming'. The effect of climate change could be, as experts attribute, the thinning of ice cover and reduction of its duration and increase in sea level due to increase in temperature. There could be changes in the variability of climate and changes in the frequency and intensity of extreme climatic events. It could be induced through human activities or natural variability. It affects all natural processes thereby influencing agrarian economies considerably. Climate change is not only a major global environmental problem but also an issue of great concern to a developing country like India.