Presentation on theme: "Tackling Groundwater Problems in Arid and Semi Arid Regions: Debating Physical Options M. Dinesh Kumar Institute for Resource Analysis and Policy Hyderabad."— Presentation transcript:
Tackling Groundwater Problems in Arid and Semi Arid Regions: Debating Physical Options M. Dinesh Kumar Institute for Resource Analysis and Policy Hyderabad
Purpose of the Session This session would discuss the various physical options for groundwater management in the context of semi arid and arid regions of India, and their scope and limitations.
Content Introduction to overview of problems Supply side options for groundwater management Scope and limitations Demand side options for groundwater management Scope and limitations Technology and cropping systems
Introduction Groundwater is an important water source in many dry regions of the world Reasons are the large stocks, and reliability of supplies, as compared to highly variable nature of surface water sources Largely treated as an inexhaustible source of water for a long time Well irrigation has great advantages over surface irrigation
Introduction contd.. In Indian sub-continent, the resource is characterized by high physical heterogeneity In Indian sub-continent, the resource is characterized by high physical heterogeneity Unconsolidated formation (mainly alluvial) Semi-consolidated formations (sedimentary sandstone Consolidated formations (hard rock formation of basalt, crystalline rocks and sandstone origin) Over-development is causing threat to groundwater supplies for irrigation and drinking uses in terms of depletion and quality deterioration in many regions
Introduction … contd. A comprehensive understanding of the management alternatives--physical, economic, institutional, policy and legal--, are lacking. It is more so for South Asian countries. Water policy makers are aware of the need for groundwater management, but often not familiar with the range of physical, economic, legal and policy instruments for groundwater management and their potential implications.
Standard instruments for controlling exploitation of groundwater Supply augmentation Water rights in the form of well permits; volumetric use rights Indirect charges through energy pricing Direct regulation of drilling; pump sets Virtual water trade Need local runoff; otherwise inter-regional water transfer Strong political system; institutional mechanisms needed Farmers are major vote banks in India Difficult to enforce in Indian context Many arid & semi arid areas are exporting virtual water
Physical approaches for groundwater management There are three different types of benefits that the society could accrue from a management intervention. They are: economic benefits; ecological/environmental benefits; and livelihood benefits. From societal point of view, a management decision would be sound, only if the aggregate of these benefits exceed the costs of proposed interventions. The aggregate benefits are a sum of the economic benefits and all the positive externalities on the society associated with the environmental/ecological and livelihood benefits.
How over-exploitation occurs? The negative consequences associated with groundwater over-exploitation are a result of net groundwater outflows exceeding the net inflows. The outflows could include: groundwater draft; evapo- transpiration of groundwater from shallow aquifers (both anthropogenic); groundwater outflows into streams and natural drainage and sinks; and regional (lateral) groundwater flows. The inflows include: natural recharge from precipitation (rainfall and snow); regional (lateral) groundwater inflows; recharge from natural water bodies such as lakes, ponds, tanks and river flows; and recharge from irrigation (both conveyance systems and irrigation water application in the field).
Contd.. The negative consequences could be: secular decline in water levels; seasonal water levels drops; intrusion of sea water in coastal aquifers; land subsidence; and deterioration of natural quality of groundwater due to leakages from saline aquifers as a result of hydraulic gradients, and geo-hydrochemical processes; and reduction in stream flows. The approaches to manage groundwater should attempt: i] reducing the outflows that are the results of anthropogenic activities, which can be managed through human actions; and, ii] increasing the components of inflows that can be manipulated by human actions.
Various supply side approaches Increasing the Inflows: Local water harvesting and recharging of groundwater through: Spreading basin method Dug well recharging (ASR) Check dams Injection wells Induced recharge Percolation tanks with recharge tube wells Watershed management
Supply side approaches Water transfers from water-rich regions for providing alternative sources of water supply California CVP North Gujarat receiving SSP waters Recycling and recharge Waste stabilization ponds Soil Aquifer Treatment (Israel)
Potential of local water harvesting and artificial recharge Groundwater depletion and water scarcity mainly occur in arid and semi arid regions Water harvesting does not work in semi arid and arid regions with: Low annual runoff, high inter-annual variability; high potential evaporation; and when basins are “closed” This is due to: Poor hydrological opportunities for harvesting and poor reliability of water supply Poor hydrological opportunities for harvesting and poor reliability of water supply Poor economic viability -ive d/s impacts due to high degree of water development -ive d/s impacts due to high degree of water development
What is the condition in India? Rainfall is low in most agriculturally prosperous regions of India, which experience depletion problems Rainfall variability is also high Evaporation rates are very high The basins in these regions are also “closed”
Physical approaches for demand management Agricultural water demand management Technological interventions Cropping system change Growing crops in regions with high water productivity due to climatic advantages
Potential impacts of micro-irrigation on groundwater use Depends on three factors: How much water could be saved using the technology at the field level What farmers do with the saved water What opportunities exist at the macro level for adoption of the technology
Constraints and opportunities in adoption of micro irrigation systems Farmers without independent source of water have least incentive to adopt MI systems Area under crops that are most amenable to MI systems in terms of water saving benefits and income benefits are low in semi arid & arid regions—7.8 M ha in India Negligible in the Indus basin area in Punjab & Haryana Absence of limits on groundwater pumping and zero marginal cost of using it reduces the economic incentives for farmers having smaller holdings in good aquifer basins In hard rock areas, well interference further reduces individual initiatives to save water in the aquifer
Constraints and Opportunities in adoption of micro irrigation systems Small operational holding of farmers increases the unit capital and operating cost of MI system Predominance of small & marginal farmers limits large- scale adoption of orchards having long gestation period In areas where power supply limits water abstraction, especially for large farmers, farmers have least incentive to go for MI systems as it does not help them expand the area In hard rock areas, with limited groundwater, farmers have high incentive to go for MI systems, as they could expand the area under the irrigated crops Current geographical spread of adoption of MIS is a testimony to this Current geographical spread of adoption of MIS is a testimony to this
Opportunities for field level water saving Field level water saving through MIS depends on agro-climate, type of MI technology, groundwater environment; crop type; and current irrigation practices Real water saving at field level would be significant in arid and semi arid basins, with deep groundwater table, with drip irrigation used for row crops Such areas include alluvial central Punjab, western Rajasthan and north Gujarat and deep water table areas of peninsular India But, applied water saving is also likely to be negligible in the Ganges plains even if crops amenable to such systems exist in this region
Opportunities for field level water saving The reasons is low non-beneficial depletion of water from soils under traditional method of irrigation Real water saving would be further lower as the deep percolation would be fully recovered The potential for water saving drip irrigation in India was estimated to be 5.9 m ha The total reduction in crop water requirement due to this was estimated to be 44 BCM.
What is the likely impact of MI systems on aggregate water use at the regional level? Often MI adoption is associated with changes in cropping system towards from traditional crops to high valued orchards--north Gujarat, Nalgonda, Jalgaon etc. Hence water saving at the field level could be high But, this can also lead to expansion in irrigated areas, particularly in situations where actual irrigated area is less than the cultivable area In areas where MI system results in “saving in applied water” alone, aggregate impact would be greater depletion of water In situations like Punjab, MI system adoption can lead to real water saving, but cropping system is not amenable
What is the likely impact of cropping system changes at regional level? Many traditional crops and dairying in semi arid and arid regions have low water productivity Replacement of traditional crops by high valued fruit crops can cut down water use even at the aggregate level due to: Significant reductions in depleted water for a unit area Absence of sufficient cultivable area to use up all the saved water at the farm level But, many farming systems are complex. Crop residues form inputs for dairying in many areas. Dairying yields high water productivity in Punjab, when compliments rice-wheat system Dairying yields high water productivity in Punjab, when compliments rice-wheat system
How far can it work in Indus and Yellow Basins? Replacing low water-efficient rice-wheat system will disturb dairying Importing fodder would increase the farming risks if done at a large scale Large scale adoption of high valued fruit crops can lead to market crash, leading to major drops in water productivity itself Also, extent to which crop shifts can take place at the regional level would be constrained by concerns of food security, and employment generation in agriculture Also, extent to which crop shifts can take place at the regional level would be constrained by concerns of food security, and employment generation in agriculture Punjab part of Indus basin and also north China plains (part of Yellow river basin) employs rural labour on large- scale; export food to water-rich regions Improving the productivity of existing crops will have to get priority
Agro-climate impact on crop water productivity In many basins, major variations in agro-climate exist spatially Indian Punjab (900 to 400 mm rainfall) Climate can affect crop yields through solar radiation and temperature It can also affect the evapo-transpiration (change in humidity, wind speed) Soil conditions will have impact on crop yields Hence, agro climate can have big impact on water productivity In Narmada basin, wheat water productivity varied widely across 9 agro climatic sub-regions In Narmada basin, wheat water productivity varied widely across 9 agro climatic sub-regions
Summary The approaches for augmenting groundwater in over-exploited areas. They include: groundwater recharge using local runoff; recharge using imported water; and, recharge using treated wastewater. In arid and semi-arid regions, the hydrological opportunities, the reliability and economic viability of artificial recharge using local runoff would be generally very low. The other two options are being practiced in developed countries, where the financial resources for such schemes are available in plenty, and the environmental value of improved groundwater environment are well recognized.
Summary Another major approach being tried world over the world is water-efficient irrigation, to raise crop water productivity. They cover: water-efficient micro irrigation devices; and efficient irrigation practices, including efficient conveyance systems. Field level real water saving due to water- efficient irrigation devices depends on the crop type, climate, soils and geo-hydrological environment Water-saving at the aggregate level would depend on a variety of socio-economic conditions including availability of extra land for cultivation; the availability of power supply vis-à-vis the amount of groundwater that can be abstracted
Summary Scope for agricultural water productivity improvement through crop shifts at the regional level would be determined by a variety of socio-economic conditions such as the contribution of the existing cropping system to regional food security, the employment generation in rural areas, and the presence of market infrastructure for high valued crops. But, in any case, the outcomes of water productivity improvement through crop shifts in terms of reduction in groundwater draft would also depend on the opportunities for farmers to expand the area under irrigation. We have also demonstrated that in some regions, opportunities might exist for enhancing water productivity by taking climatic advantages
Heterogeneity in geo-hydrology
Will Water Harvesting and Local Recharging Benefit Water- Scarce Regions?
Sr. No Type of Recharge Structure (Life in years) Expected Active Life of the System Estimated Recharge Benefit (TCM) Capital Cost of the Structure (in Lac Rs.) Cost of the Structure per m 3 of water (Rs/m 3 ) Annualiz ed Cost* (Rs/m 3 ) 1Percolation Tank Check Dam Recharge Trench/Shaft/ Sub-surface Dyke Estimated Unit Cost of Artificial Recharge Structures Built under Pilot Scheme of CGWB
Effect of Watershed Interventions on Run- Off Effect of Watershed Interventions on Run- Off Ghelo-Somnath Rainfall and Reservoir Inflows Year Total Rainfall, cm Total Runoff, cm
Water Productivity in Crops and Milk Production
Water productivity in crops and dairying in north Gujarat
Vibrant dairy economy is a constraint to saving groundwater in north Gujarat Milk Production and Aggregate Groundwater Use with WST Min Cur Prod Proportion of Current Production of Milk % Saving in Water Use
Water productivity in wheat in different regions of narmada basin
Current scale of adoption of MI systems Name of States Area under Total Area (ha) DripSprinkler Rajasthan Maharashtra Haryana Andhra Pradesh Karnataka Gujarat Tamil Nadu West Bengal Madhya Pradesh Chhattisgarh Orissa Uttar Pradesh Punjab Kerala Sikkim Bihar Others India Total