Tube wells may not be so ‘well’ later
Tube wells, as we know, help us extract groundwater. Groundwater forms a base for agriculture and crop irrigation. It is widely extracted and used for daily routines such as bathing and washing clothes and dishes in rural areas. Aquifers are a ready-to-go source of water for millions across India. Moreover, groundwater, due to infiltration, has fewer impurities in it as compared to surface water so it is widely used for drinking purposes. It is also an integral part of the hydrological cycle and contributes to maintaining it. Furthermore, groundwater is a source of land vegetation so it lends a hand in maintaining the land cover.
But how do we actually define groundwater and how does the whole groundwater system work? Groundwater, in scientific terms, would be water that exists underground in saturated zones beneath the land surface. The upper surface of the saturated zone is called the water table. Groundwater makes its way through the cracks and crevices in soil and rocks. It is pulled by gravity and the force of water above it pushes it down further. Water moves and enters an aquifer (recharge zone) and it reaches a point where it exits the aquifer (discharge zone). The slope of the water table is called the hydraulic gradient which determines the direction in which the groundwater will flow. Groundwater tends to flow slowly as compared to surface water.
The term ‘Climate Change’ is well-known across the planet. But what is climate exactly? How do we define Climate and its change? Climate, according to Intergovernmental Panel on Climate Change (IPCC), is the average weather in terms of its mean and variability over a certain period and a certain area; and a statistically significant variation of the mean state of the climate or of its variability lasting for a decade or longer is referred to as Climate Change. The reason for such shifts can be natural like variations in the solar cycle but since around the time of the Industrial Revolution, anthropogenic causes such as burning fossil fuels have become the main drivers for Climate Change. The well-experienced effect of climate change would be the ‘greenhouse effect’. It is the phenomenon where heat is trapped in Earth’s atmosphere due to an increase in the amount of greenhouse gases such as Carbon Dioxide or Methane. These gases trap infrared radiation and reflect it back to Earth. The concentration of such gases increases as a result of the increase in emissions due to the burning of fossil fuels as mentioned above.
Factors Affecting Groundwater Levels and Climate Change
i) Groundwater
Before we jump to the relationship between groundwater and climate change, we'd need to see what affects each of them individually. Groundwater and its recharge, on a large scale, is affected by the water cycle. Major factors that affect the hydrological cycle are changes in regional temperature and precipitation. These parameters determine how much water reaches the surface, gets back to the atmosphere, gets stored as snow or ice, infiltrates groundwater, runs off the land and eventually contributes to rivers and streams. Changes in these two parameters directly affect the water cycle and thus, groundwater. To add, evapotranspiration is also a factor which adds to the water balance of an area. The rate of evapotranspiration depends largely on the vegetative cover of the land. Increased consumption of groundwater for irrigation affects the level of the water table significantly. Extracting water faster than it can be recharged causes groundwater levels to decline over time. Other factors like land degradation and natural disasters also determine groundwater levels. For example, most of the water from floods runs off as ‘rejected recharge’ (discharge of water due to aquifer being full and can’t accept it) and it can’t be utilised.
ii) Climate Change
Climate change is a very broad aspect to look at. A few of the direct causes of climate change are, generating power which includes powering homes, forming fuels and manufacturing goods; other direct causes are deforestation and consuming more energy than we need. Furthermore, increased usage of power, for example, using motors for pumping of water increases emissions as it consumes fuel or electricity. An average electric motor produces 0.4062 kgCkWh^-1 (kilogram Carbon kilowatt per hour) whereas a diesel motor produces 0.732 kgCkWh^-1. At the rate groundwater is extracted, emissions are high. Such emissions contribute to the cumulative emissions being released into the atmosphere. This includes greenhouse gases like carbon dioxide, nitrous oxide and many others. These greenhouse gases lead to the greenhouse effect (discussed above). Accumulation of trapping of heat raises Earth's temperature and this warming for the longer term leads to the phenomenon of Global Warming.
Effects of Climate Change
Global Warming is one of the deadly effects of Climate Change. This in turn causes:
i) Increase in Earth’s temperature
An increase in the concentration of greenhouse gases traps more heat raising the global surface temperature. IPCC estimates the temperature of Earth has increased 0.6+- 0.2 degree Celsius since 1861. According to IPCC (2001), landmass below Indo- Gangetic plains is likely to experience an increase of 0.5-1 degree Celsius increase between 2021- 2029 and a 3.5-4.5 degree Celsius increase between 2090-2099. Predictions claim the climate to increase by 2-4 degrees Celsius in the next 100 years.
ii) Increased Droughts
An increase in temperature changes the hydrological cycle as we saw before. This causes a change in water availability in certain regions. This leads to a shortage of water in water-stress regions proceeding to an escalated risk of agricultural and ecological drought. This advances to a shortage of food and a loss of ecosystems. Moreover, heavy winds over drought regions can cause dust storms. 19% of large cities are already facing a high risk of drought. These droughts affect the agriculture sector the most. More than 80% of damage caused by droughts shows an effect on the agricultural sector.
iii) Increased storms
An increase in temperature leads to more evaporation from water bodies and increased transpiration from plants. This spike of moisture in the atmosphere causes extreme rainfall and flooding. Warming of the ocean sparks hurricanes, cyclones and typhoons. Warm oceans become a feeding ground for such natural disasters. Over the years, the Power Dissipation Index (measurement of intensity and duration of wind speed of storms) has increased. Recent studies predict that storms in the future will be more destructive, last longer and cause landfalls more frequently.
iv) Rising, warming oceans
Global Warming is causing glaciers and icebergs to melt which raises the level of seawater. Moreover, the warming of the sea causes it to expand which takes up more volume. To add a cherry on top, oceans absorb a lot of carbon dioxide from the air causing them to turn acidic hindering the normal functioning of marine ecosystems. Warming oceans become a feeding ground for natural disasters like cyclones, typhoons and hurricanes as we discussed earlier.
v) Loss of Species
As I mentioned earlier, ocean acidification hinders the normal functioning of ecosystems and major ones like corals which are 'rainforests of the ocean' are destroyed. Rising temperatures also pose a risk to survival for creatures on land as they are not adapted to this warming and can't adapt anytime soon enough. Disruption of the food web is a common effect of these changes. This causes a loss of species. This might also force species to migrate to higher altitudes where the temperature is suitable for their survival. Similarly, an increase in sea levels can cause keystone fisheries to relocate or die. Due to such changes, species are not able to adjust accordingly and the ecosystem and species become vulnerable. Due to asynchronous behaviour, migration timings, food availability and breeding go haywire. All of this causes ecosystem misbalance and leads to species and habitat loss.
vi) Food shortage
Changes in climate and extreme weather conditions cause loss of agricultural land, livestock and fisheries. Acidification of the ocean puts fisheries at risk and thus food shortage over the long term. As we discussed earlier, droughts affect the agriculture sector way more than any other sector. This, in turn, leads to crop failure, loss of livestock and rising commodity prices. Crops such as Rice and Wheat which require high amounts of water will be highly affected. The demands for food will not be met. This overtime would lead to food shortage.
In addition to this, we’ll be looking at a few over effects when discussing certain topics.
Relation of effects of climate change on groundwater
i)Increased temperature
We have now looked at factors that affect climate and groundwater. Groundwater recharge is mainly dependent on aquifers and the soil type and quality. Due to rising temperatures, evaporation from these water bodies increases, which leaves less water for the recharge of the water table. Increased evapotranspiration from trees causes them to take up more water from the ground to compensate for the loss thus decreasing levels of groundwater. Furthermore, soil moisture decreases due to increased temperature which increases the risk of drought.
ii)Land degradation and aggravation
Climate change which happens due to deforestation and retrogressive succession (turning of a complex ecosystem into a simpler one) of ecosystems, causes a reduction in vegetative cover and fragmentation of habitat leading to the loss of species. A decrease in vegetative cover makes the land more vulnerable during floods and increases the surface runoff of water. During floods, barren or agricultural lands can't hold onto soil particles strong enough, so the sediments which consist of minerals, get washed away leading to land degradation. If the vegetative cover is present, plants hold on to soil particles strongly and help retain a lot of water which doesn't happen in the case of barren lands which decreases groundwater recharge. On the other hand, land aggradation due to the deposition of these sediments downstream at different aquifers lowers the aquifer's depth. This causes the aquifers to hold less water than their original capacity which ends up lowering the infiltration of water and thus groundwater recharge.
iii)Melting of snow caps and icebergs
Due to the melting of glaciers and icebergs, the sea level rises. This rise in sea level causes it to infiltrate aquifers which lie near coastal areas. This infiltration causes groundwater in coastal aquifers to turn salty. The melting of snow caps and icebergs increases the flow of rivers and their levels. This increases the chances of flood. Along with this, the sea level increases which leads to more water being evaporated (more humidity) due to increased temperature. Increased humidity causes an increase in the frequency of cyclones and typhoons since warming oceans are a feeding ground for them. Events like cyclones and typhoons cause a lot of destruction including disruption of ecosystems and uprooting of trees which causes the land to barren and indirectly affect groundwater recharge.
iv)Droughts and floods
Areas with less vegetative cover and fewer water bodies contribute less moisture to the environment, leading to less precipitation. Pair that up with temperature increase due to global warming and you get increased water stress and thus, droughts. These droughts cause people to consume more groundwater and thus decreasing groundwater levels. Fewer water bodies would mean less recharge of groundwater. Droughts can slow groundwater level recovery in agricultural areas compared to forested areas. As we discussed earlier, droughts can lead to crop failure and livestock loss.
Floods, in addition to land degradation, cause excess water to reach an area. Most of this water runs off the surface and water that seeps in turns into rejected recharge. Storms induce floods which cause destruction in urban, forested and agricultural land areas. This in turn decreases land cover, increases runoff and decreases recharge. Floods, similar to droughts, can cause crop failure and loss of livestock and fisheries.
v)Precipitation and runoff
An increase in precipitation in some regions causes floods and we discussed above how floods affect the land. Increased rainfall would mean an increase in plant growth and leaf size which would alter the recharge rate (Kundzewicz and Doll 2007). As the effects of climate change intensify, temporal change in rainfall is guaranteed. This means an intense and large amount of rainfall during monsoon will be followed by long dry periods. This variability in rainfall increases the run-off coefficient (runoff/precipitation). Thus, variability in rainfall can cause a decrease in recharge (Carter 2007).
vi)Vegetative cover
Depending on the vegetative cover, the amount of groundwater that percolates is determined. A high vegetative cover would increase recharge as more water is retained by the soil and less is lost as runoff.
A less vegetative cover would mean less water retained by the soil and more lost as runoff thus decreasing groundwater recharge. Regardless of this, Carter (2007) argues that the conversion of forested areas to agricultural land will increase recharge by a factor of 10. This is due to more water reaching the surface which would normally get blocked by the canopy. On top of this, increased vegetation would mean increased evapotranspiration which would further lower infiltration rates.
Relation of Climate Change and Groundwater (Indian Context)
History of Groundwater in India:
India has been a groundwater powerhouse since the past. In 1890, India had 12 million hectares (ha) of irrigated land as compared to 3 million ha in the United States, 2 million ha in Egypt and 1.5 million ha in Italy. British India, in around 1810, built canals and reconfigured the river basins. Over time, the agriculture sector demanded more water and it increased exponentially after the 1960s. By the 2000s, tanks and canal systems were not enough to sustain the agricultural demands so groundwater wells were built. This led to an increase in the pumping of groundwater. Currently, agricultural states in the northern regions like Haryana and Punjab are devoid of groundwater due to overexploitation of it over the years. Climate change is posing new challenges and uncertainties in maintaining groundwater levels.
Groundwater storage is declining across northern regions which have near 0 groundwater storage. This suggests over-exploitation and use of water way faster than it can be recharged including areas with huge river basins like Indo-Gangetic plains.
India’s Hydro-Climatic Conditions Due to Climate change, there will be certain changes in the hydrology of India. Due to increasing temperature, snow caps will melt and will increase the stream of Indo-Gangetic basins. This will continue till 2030 and later on, the basin would face a reduction in the supply. As compared to the basin, the rest of India will receive more rainfall in the future. As we discussed earlier, the temperature of the basin is predicted to rise by 0.5-1 degree Celsius in 2021-2029 and by 3.5-4.5 degree Celsius increase in 2090- 2099(IPCC 2001). The guaranteed temporal variability mentioned earlier will be accompanied by a 5-10% increase in precipitation in the Western Ghats (IPCC 2001). This leads to increased ‘dry’ and ‘wet’ days (Gosain and Rao 2007). With an increase in precipitation, runoff increases. There will be a 5-20% increase in surface runoff as compared to 1900-the 1970s between
years 2041-2060 (Milly et al (2008)).
Time Averaged Map produced via NASA’s Giovanni
Satellite Data Used: TRMM
This map shows the increase in the Western Ghats of precipitation as compared to the rest of India and this number is predicted to increase. With the rising temperature, soil moisture would decrease and evapotranspiration would increase. This increase in evapotranspiration in crops would lead to more frequent irrigation; especially Rabi (summer crops). Due to variability in precipitation and temporal variability, Kharif (monsoon crops) face a higher risk of floods and droughts.
Time Series, Area Average Graph produced via NASA’s Giovanni
Satellite Data Used: AIRS
The graph shows the gradual rise in air temperature over the years.
What can be done?
The solution to groundwater depletion and climate change’s effect on it is management and an increase in the capacity of reservoirs. Rethinking storage and transitioning to aquifers from surface water storage is more relevant. Proactive maintenance of the demand and supply side in relation to groundwater is one of the applicable ways groundwater levels and storage can be managed. Proactive maintenance (incorporating effective means to manage agricultural water demand as well as enhance natural groundwater recharge.) of aquifer storage should be prioritised by policymakers. In the absence of groundwater development, water that could have contributed to recharge gets converted to runoff. Thus, groundwater development is needed. The best way to counter all this would be to mitigate climate change as much as possible.
Groundwater and Climate Change are connected in primary and secondary ways. Groundwater is important for us and is used by millions of people around India. Groundwater is water that exists underground in saturated zones beneath the land surface. The upper surface of the saturated zone is called the water table. The climate is the average weather in terms of its mean and variability over a certain period and a certain area, and a statistically significant variation of the mean state of the climate or of its variability lasting for a decade or longer is referred to as Climate Change. Climate change causes the greenhouse effect which is the trapping of heat in the earth’s atmosphere. Climate change is caused due to generation of power, powering of homes, burning fossil fuels and increased consumption of fuel and electricity. Groundwater is affected by several factors including increased consumption, increased temperature, rainfall variability, temporal variability, evapotranspiration rates and many more. All of this is somewhere due to Climate Change. It is posing new challenges and uncertainties in maintaining groundwater levels. Climate change causes increase in temperature, water levels, droughts, floods and storms. It also causes land degradation, aggradation, melting of snow caps and icebergs and ecosystem misbalance leading to the loss of species. Relating groundwater and Climate Change, the vegetative cover is a determining factor for groundwater recharge. Furthermore, changes in rainfall and temperature cause changes in leaf size and growth rate of plants which affects recharge. Along with this, change in river flows, change in intensity and variability of precipitation and changing temperature, all influence natural recharge rates. With increased temporal variability, runoff increases which in turn causes a rise in the run-off coefficient. Thus, higher variability in rainfall causes decreases in groundwater recharge. With the melting of snow caps, the flow of rivers increases which spike up the chances of floods.
Groundwater development is significant in preventing water to escape as runoff. Last but not the least, mitigating climate change in any small way possible would prove very beneficial for groundwater and the world in general.
~ Ksheetij Pandey
References
1. Climate Change and Its Impact on Groundwater Resources C. P. Kumar Scientist ‘F’, National Institute of Hydrology, Roorkee – 247667 (Uttarakhand)
2. Towards best practice for assessing the impacts of climate change on groundwater I. P. Holman & D. M. Allen & M. O. Cuthbert & P. Goderniaux
3.https://www.usgs.gov/faqs/whatgroundwater#:~:text=Groundwater%20is%20water%20that%20exists,does%20not%20form%20underground%20rivers.Un.org
4.https://www.sciencedirect.com/science/article/abs/pii/S0022169413004800
5. http://snr.unl.edu/data/water/groundwater/realtime/satuate.aspx
6.https://www.un.org/en/climatechange/whatisclimatechange#:~:text=Climate%20change%20refers%20to%20long,like%20coal%2C%20oil%20and%20gas.
7. https://www.nps.gov/jomu/learn/nature/climate-change.htm
8. https://www.igi-global.com/dictionary/application-of-software-in-soil-and-groundwater-rechargeestimation-in-ilorin-nigeria/71848#:~:text=1.,full%20and%20cannot%20accept%20it.
9.https://19january2017snapshot.epa.gov/climateimpacts/climateimpactsecosystems_.html#:~:text=Climate%20change%20can%20alter%20where,wildfires%2C%20floods%2C%20and%20drought.
10.https://www.un.org/development/desa/dpad/publication/undesapolicybrief102populationfoodsecurity-nutrition-and-sustainable-development/
11. Climate change and groundwater: India's opportunities for mitigationand adaptationTushaar Shah 1
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