Presented by;Abhishek Kumar414ER2018Earth & Atmospheric Sciences

Impact of climate change on groundwater

abhi.gly@gmail.com

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Groundwater in Hydrologic cycleWhat is Climate Changes?Hydrological Impact of Climate changeImpact of Climate Change On GroundwaterClimate change Scenario for Groundwater in IndiaMethodology to Assess the Impact of climate Change On Groundwater

PRESENTATION OVERVIEW

Why include Groundwater in climate changes studies?Although groundwater accounts for small percentage of Earths total water,Groundwater comprises approximately thirty percent of the Earths freshwater.Groundwater is the primary source of water for over 1.5 billion people worldwide.Depletion of groundwater may be the most substantial threat to irrigated agriculture.

Natural groundwater recharge accounts for:Components of the hydrologic cycle:Precipitation, Evaporation, Transpiration, Recharge,And Baseflow.Heterogeneity of geological structures, local vegetation, and weather condition natural GrounDwater recharge

Groundwater overdraft / mining / subsidenceWaterloggingSeawater intrusionGroundwater pollutionProblems with groundwater

Hazardous industrial wasteLeachate from landfillsAgricultural activities such ac the use of fertilizer and pesticidesThe total volume that may be withdrawn annually from the aquifer.The location of pumping and artificial recharge wells, and their rates.Decisions related to groundwater quality.Management of a groundwater system, means making such decisions as:Groundwater contamination by:

IPCC usage: -Any change in climate over time, whether due to natural variability or from human activity.

Alternate: -Change of climate, attributed directly or indirectly to human activity, that -Alters composition to global atmosphere and -Is in addition to natural climate variability observed over comparable time periods What is climate change?

Both natural and anthropogenic factors control climate change .

climatic conditions were not the same throughout the history of the Earth. Natural causes:Earths axial and orbital changes changes in the strength of the Sun plate movementsasteroid collision and chemical weathering

Factors causing climate change

Climatic fluctuations all through the geological timescale

Earths axial and orbital changes The change in the tilt of the axis of the Earth affects the amount of solar radiation received on the surface it shows a latitudinal difference and thus results in seasons on Earth The Earths axial tilt at present is 23.5 and varies between 22.2 and 24.5. Increase in the tilt amplifies seasonal differences and decrease in the tilt results in the reduction of seasonal differences and thus affects Earths climate.Changes in the strength of the Sun:The strength of the Sun is measured by the number of sunspots visible on its surfaceThe concentration of CO2 decreases with the cooling of oceans and increases with their heating, proving that the Sun is a primary driver of climate on Earth.Plate tectonics:The position of south magnetic pole during 430 m.y. ago coincides with the climate change that has been observed, which showed the occurrence of large-scale glaciations in the modern-day Sahara Desert .Volcanic eruptions also change the composition of the atmosphere by ejecting SO2, CO2, water vapour and pyroclastic materials .

Asteroid collision: large-sized (greater than 10 km radius) impacts are rare and arrive on the Earth only after every 50100 million years.The Earth has experienced such events during the PermianTriassic boundary and at the CretaceousTertiary boundary which resulted in mass extinctions and in the beginning of a new era Chemical weathering: The changes in CO2 concentration in the atmosphere can be related to the chemical weathering processes, which include hydrolysis and dissolution.

Groundwater is directly affected by changes in the rate of precipitation and evapotranspiration.The response of groundwater to climate change may be less compared to surface water, however, it is still a matter of concern because groundwater is one of the largest available resources of freshwater and potable water on Earth. It is estimated that approximately 30% of global freshwater is present in the form of groundwater.Todd divided the groundwater occurrence in two zones zone of aeration and zone of saturation.The effect of climate change on both the zones has been discussed in the followingZone of aeration Soil water zone Vadose zone Zone of saturation Effect of climate change on groundwater zones

Soil water zone: This zone is important as it supports vegetation and all biogeochemical reactions. Climate change has an adverse effect on this zone. Higher temperature leads to higher evapotranspiration rates, resulting in less moisture content in this zone. Little or no moisture in the soil leads the penetration of solar radiation into the deeper soils and increased dryness in soils, resulting in severe droughts .The high precipitation in wet climate change scenario will increase surface run-off and in promoting rapid soil erosion.Less infiltration, high evapotranspiration and high run-off will have a great impact on the water availability in this zone, which will affect the entire plant and animal kingdom. Because of change in evapotranspiration patterns in this zone, the rainfall pattern will also be affected. The transpiration process which holds 8090% of overall evapotranspiration on Earth will show various changes depending on the regional vegetation.Zone of aeration

Vadose zone: Changes in vadose zone due to climate change can be computed by studying the variations in major cations, an-ions, trace elements and isotopes from the pore water.Due to increase in surface temperature, groundwater temperature will increase. The change in temperature will affect pore water chemistry, residence time and volume of water in matrix and fractures, and thus the composition of the water.The increase in recharge rate will help in mobilizing the contaminants into greater depths. As an example, in semiarid and arid regions, increased infiltration can mobilize large, pore-water chloride and nitrate reservoirs affecting the quality of water.The diurnal temperature fluctuations may be detectable at depths of less than 1 m in the unsaturated zone and seasonal fluctuations at depths of 10 m or more, indicating that that the climate change effects depend on depth and are slow in the deep vadose zone.

Zone of aeration

Groundwater in the saturated zone is important as it is less polluted and has no effects of evapotranspiration.The sensitivity of this zone depends on the depth of the water table; shallow aquifers are more vulnerable to cli-mate change than deeper aquifers.This zone responds to climate change by showing changes in its amount, quality and flow of water depending on the trends of precipitation, evapotranspiration, recharge and discharge.It is generally observed that climate change has less effect on this zone in comparison to human activities on groundwater exploitation, such as excessive pumping, reduction in recharge rate and contamination.

Zone of saturation

Confined and unconfined will show alterations in some of their properties during climate change. It has been noticed that severe dry periods can alter the properties of aquifers such as transmissivity and storativity.During dry periods, the conductive channels such as fractures and fissures may become desaturated and the pressure pulse of water within the aquifer will be transmitted slowly, whereas during the wet season, fractures get fully saturated and transmit pressure pulse rapidly. Thus, the changes in recharge pattern will affect the specific storage of an aquifer.In case of extreme aridity, their vulnerability becomes higher if the potentiometric surface falls below the upper confining beds and results in converting confined aquifers to unconfined aquifers.

Effect of climate change on aquifers

Groundwater Recharge:The changes in recharge patterns will affect discharge patterns, which will have a direct impact on groundwater supplies and on surface water availability. In a cold or wet and coldwet scenario, the relationship is directly proportion-al, i.e. high temperature results in high precipitation and high recharge.In case of dry scenario, the temperature and precipitation are inversely related to each other, as high temperature will result in less rainfall. Hence, the effects in case of dry scenario will be severe, implying that the aquifers of semiarid and arid regions are more vulnerable to climate change.Changes in recharge patterns will also alter the quality of water by affecting geochemical reactions and movement of water in the vadose zone.Various types of aquifers will be recharged differently. The main types are unconfined and confined aquifers.

Effect of climate change on recharge and discharge

Groundwater Recharge:An unconfined aquifer is recharged directly by local rainfall, rivers, and lakes, and the rate of recharge will be influenced by the permeability of overlying rocks and soils.Unconfined aquifers are sensitive to local climate change, abstraction, and seawater intrusion. However, quantification of recharge is complicated by the characteristics of the aquifers themselves as well as overlying rocks and soils.A confined aquifer, on the other hand, is characterized by an overlying bed that is impermeable, and local rainfall does not influence the aquifer. It is normally recharged from lakes, rivers, and rainfall that may occur at distances ranging from a few kilometers to thousands of kilometers.Determining the potential impact of climate change on groundwater resources, in particular, is difficult due to the complexity of the recharge process, and the variation of recharge within and between different climatic zones.

Effect of climate change on recharge and discharge

Groudnwater Discharge:Under wet climate scenarios, run-off is considered as a most sensitive component and the combined effect of in-creased precipitation and high discharge will increase the risk of flooding.Under dry climate scenarios, recharge will be the most sensitive component as evapotranspiration will increase while both recharge and discharge will decrease in all seasons, resulting in decline in ground-water level.Increased discharge from melting of glaciers in the Himalayas will increase the risk of flooding in the catchment areas affecting major parts of North India, Pakistan and Bangladesh. Due to changes in discharge, the quality of groundwater will be adversely affected, since during high discharge all the pollutants will be mobilized and may reach groundwater level.In the case of a dry climate scenario, generally the water level will fall and this will affect the needs of the people and may result in increased use of energy to ex-tract water.The increase in groundwater pumping and loss of groundwater storage from aquifers resulted in land subsidence in many Asian cities such as Osaka and Bangkok. In future, the increase in dis-charge and decrease in recharge will make land subsidence a much bigger problem

Effect of climate change on recharge and discharge

The groundwater quality relates to the physical, chemical and biological properties of the aquifers, which are controlled by climatic fluctuations. changes in the recharge rate and the groundwater temperature in the vadose zone affect its pore water chemistry, contaminant transport and residence time, thus affecting the quality of water.Under a climate change scenario, the following events can deteriorate the groundwater quality. During the wet scenario, increased infiltration can mobilize large pore-water chloride and nitrate reservoirs in the vadose zone of semiarid and arid regions.Increase in recharge leads to the dissolution of carbonates; increase in Ca content may increase the hardness of groundwater.During a dry scenario, the increase in total dissolved solids may deteriorate the groundwater quality by increased salt content

Effects of climate change on groundwater quality

The three major reasons for the sea-level rise are: expansion of oceans on warming, increase in discharge due to melting of glaciers and excessive pumping due to human settlements along the coasts.The rise in sea level is said to have a great impact on the man-grove forests of the world and aquatic life, affecting the fish stocks and planktons1,28. It is estimated that 30% of coral reefs could be lost in the next 10 years, which will affect the food web of the aquatic environment.

Effect of climate change on sea-water intrusion

Indias groundwater status and utilization India accounts for 2.45% of land area and 16% of the world population, whereas only 4% of freshwater re-sources of the world are available in India, of which 38.5% is groundwater.India was utilizing less groundwater compared to USA and Europe, but by 2000, India utilized around 220230 billion m3 year-1, over twice that the USA .The per capita water availability is continuously declining from 5176 m3 in 1951 to 1820 m3 as on 1 March 2001 and 1703.6 m3 on 1 March 2005.

Effect of climate change on groundwater resources of India

Climate change effect on Indian groundwater resources The levels are continuously falling down. Groundwater level in Gujarat, Rajasthan, Punjab, Haryana and Tamil Nadu has shown a critical decline.Groundwater decline has been registered in 289 districts of India. The water table in Ahmedabad is falling at a rate of 45 m every year; in some parts of Delhi a lowering of 10 m has been noticed.Due to melting of the Himalayan glaciers, the Indo-Gangetic Plains will experience increased water dis-charge till 2030s but will face gradual reductions thereafter. Sea-water intrusion has been observed in several coastal states of India, such as Tamil Nadu, Puducherry and Gujarat (Saurashtra), which is not only engulfing the land but also the groundwater reservoirs India is highly sensitive to climate change in terms of its effect on water supply for irrigation needs.

Effect of climate change on groundwater resources of India

Behavioural and structural adaptations:using buckets and not showers for bathing and use of recycled water for agriculture.Structural adaptation implies building infrastructure or techniques that can minimize the risk of climate change on groundwater and increase storage capacity of aquifers.rainwater harvesting, artificial recharge of aquifers, underground dams, reservoirs and check dams, etc.Defining groundwater risk zones and climate change mapping:Spatiotemporal effect of climate change on aquifers should be assessed and based on this risk assessment of each aquifer should be rated and actions and policies should be designed accordingly.Climate change mapping on different resources will give better results and answers about the vulnerability and risks involved over time for a specific area Mitigation strategies to reduce effects of climate change

Promoting afforestation:Trees are the sinks for CO2 on the Earth, and to minimize the effect of global warming, afforestation is the best way, with the aim of reducing deforestation.Land-use development planning should emphasize on planting more trees and increasing recharge area.CO2 sequestration:Due to unusually large amounts of CO2 added to the atmosphere, carbon cycle is insufficient to maintain the balance.annual carbon emissions from the use of fossil fuels in USA accounts for 1.6 giga tons, whereas the natural annual uptake is only about 0.5 giga tons, i.e. 1.1 giga tons per year remains in the atmosphere.This extra CO is responsible for global warming, which can be trapped in forests, grasslands, oceans and in the sedimentary formations such as coals.this sequestration processes is also beset with many environmental issues and concerns

Mitigation strategies to reduce effects of climate change

Bouraoui et al. (1999)Presented a general approach to evaluate the effect of potential climate changes on groundwater resources.A general methodology is proposed in order to disaggregate outputs of large-scale models and thus to make information directly usable by hydrologic models.Two important hydrological variables: rainfall and potential evapotranspiration are generated and then used by coupling with a physically based hydrological model to estimate the effects of climate changes on groundwater recharge and soil moisture in the root zone. Status of Research & case Studies

Sherif and Singh (1999)Investigated the possible effect of climate change on sea water intrusion in coastal aquifers.Using two coastal aquifers, one in Egypt and the other in India, this study investigated the effect of likely climate change on sea water intrusion.Under conditions of climate change, the sea water levels will rise which will impose additional saline water heads at the sea side and therefore more sea water intrusion is anticipated.A 50 cm rise in the Mediterranean sea level will cause additional intrusion of 9.0 km in the Nile Delta aquifer.The same rise in water level in the Bay of Bengal will cause anadditional intrusion of 0.4 km

Status of Research & case Studies

Ghosh Bobba (2002)Analysed the effects of human activities and sea-level changes on the spatial and temporal behaviour of the coupled mechanism of salt-water and freshwater flow through the Godavari Delta of India.The density driven salt-water intrusion process was simulated with the use of SUTRA (Saturated-Unsaturated TRAnsport) model.The results indicate that a considerable advance in seawater intrusion can be expected in the coastal aquifer if current rates of groundwater exploitation continue and an important part of the freshwater from the river is diverted for irrigation, industrial and domestic purposes. Status of Research & case Studies

Brouyere et al. (2004)Developed an integrated hydrological model (MOHISE) in order to study the impact of climate change on the hydrological cycle in representative water basins in Belgium.This model considers most hydrological processes in a physically consistent way, more particularly groundwater flows which are modelled using a spatially distributed, finite-element approach.The groundwater model is described in detail and results are discussed in terms of climate change impact on the evolution of groundwater levels and groundwater reserves.Most tested scenarios predicted a decrease in groundwater levels in relation to variations in climatic conditions. Status of Research & case Studies

Holman (2006)Described an integrated approach to assess the regional impacts of climate and socio-economic change on groundwater recharge from East Anglia, UK.Important sources of uncertainty and shortcomings in recharge estimation were discussed in the light of the results.Changes to soil properties are occurring over a range of time scales, such that the soils of the future may not have the same infiltration properties as existing soils.The potential implications involved in assuming unchanging soil properties were described. Status of Research & Case Studies

Mall et al. (2006)Examined the potential for sustainable development of surface water and groundwater resources within the constraints imposed by climate change and future research needs in India.He concluded that the Indian region is highly sensitive to climate change.The National Environment Policy (2004) also advocated that anthropogenic climate changes have severe adverse impacts on Indias precipitation patterns, ecosystems, agricultural potential, forests, water resources, coastal and marine resources.Large-scale planning would be clearly required for adaptation measures for climate change impacts, if catastrophic human misery is to be avoided. Status of Research & Case Studies

Ranjan et al. (2006)Evaluated the impacts of climate change on fresh groundwater resources specifically salinity intrusion in five selected water resources stressed coastal aquifers.The annual fresh groundwater resources losses indicated an increasing long-term trend in all stressed areas, except in the northern Africa/Sahara region.They also found that precipitation and temperature individually did not show good correlations with fresh groundwater loss.They also discussed the impacts of loss of fresh groundwater resources on socio-economic activities, mainly population growth and per capita fresh groundwater resources. Status of Research & Case Studies

Toews (2007)Modeled the impacts of future predicted climate change on groundwater recharge for the arid to semi-arid south Okanagan region, British Columbia.Climate change effects on recharge were investigated using stochastically-generated climate from three GCMs.Spatial recharge was modelled using available soil and climate data with the HELP 3.80D hydrology model.A transient MODFLOW groundwater model simulated rise of water table in future time periods, which is largely driven by irrigation application increases. Status of Research & Case Studies

These studies are still at infancy and more data, in terms of field information, are to be generated. This will also facilitate appropriate validation of the simulation for the present scenarios.In summary, climate change is likely to have an impact on future recharge rates and hence on the underlying groundwater resources. The impact may not necessarily be a negative one, as evidence by some of the investigation.Quantifying the impact is difficult, and is uncertainties present in the future climate predication. However, it is clear that the global warming threat is real and the consequences of climate change phenomena are many and alarming. Concluding Remarks on the Research Studies

The methodology consists of three main steps.

To begin with, climate scenarios can be formulated for the future years such as 2050 and 2100.

Secondly, based on these scenarios and present situation, seasonal and annual recharge are simulated with the UnSat Suite (HELP module for recharge) or Wet Spass model.

Finally, the annual recharge outputs from UnSat Suite or Wet Spass model are used to simulate groundwater system conditions using steady-state groundwater model setups, such as MODFLOW, for the present condition and for the future yearsMethodology to Assess the Impact of Climate Change onGroundwater Resources

The influence of climate changes on groundwater levels and salinity, due to:a. Sea level riseb. Changes in precipitation and temperatureMethodology1. Develop and calibrate a density-dependent numerical groundwater flow model that matches hydraulic head and concentration distributions in the aquifer.2. Estimate changes in sea level, temperature and precipitation downscaled from GCM outputs.3. Estimate changes in groundwater recharge.4. Apply sea level rise and changes in recharge to numerical groundwater model and make predictions for changes in groundwater levels and salinity distribution.Methodology to Assess the Impact of Climate Change onGroundwater Resources

Divide the globe into large size gridsPhysical equationsLots of computingPredict the climatological variables Global climate models (gcm)

Five step process outline by Glieck & Frederick (1999)Look at several Global Climates Models (GCMs) and look for consensus & rangesDownscale to level needed (statistical and dynamical methods)Apply impact ranges to hydrologic modelingDevelop systems simulation modelsAssessment of the result (historic and GCMs) at representative time framesGlobal climate models translated to local impacts

Threats:- quality and quantity of the groundwater resources. GHGs:-its effect on continental surface water, oceans, ocean productivity, vegetation, etc. In addition, it has a significant effect on the energy cycle and groundwater. We perceive the immediate climate change effects in terms of floods, drought conditions, glacial melts, etc. The effect of climate change is significantly more on the semiarid, arid and coastal aquifers of the world.In India, the vulnerability is extremely high because of overexploitation of the groundwater and accompanied land subsidence in urbanized areas. Groundwater is one of the most utilized resources in India for drinking and irrigation purposes. better planning and management of this vital resource. Conclusion

IPCC, Climate Change 2007 Synthesis Report, An Assessment of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK, 2007, p. 73. Global warming, 2010; http://earthobservatory.nasa.gov Frederick, K., Climate Issues, Brief No. 3, Water Resources and Climate Change. Resource for the Future, 1997, pp. 111. Todd, K. D., Groundwater Hydrology, John Wiley, New York, 1980, 2nd edn, p. 527. Singh, R. D. and Kumar, C. P., Impact of climate change on groundwater resources, 2010; www.angelfire.com/nh/cpkumar/ publicationKumar, R., Singh, R. D. and Sharma, K. D., Water resources of India. Curr. Sci., 2005, 89, 794811. Climate change policies in the Asia-Pacific, re-uniting climate change and sustainable development. IGES, 2008, pp. 159180. Carbon sequestration to mitigate climate change, 2008; www. usgs.gov

References