Water, Mitigation And Climate Change

Freshwater systems are an indispensable part of climate action, because mitigation, which is the cutting avoidance or absorption of carbon emissions, is not possible without water. Water therefore forms the central focus of climate action.

Only 3% of the world’s water resources is freshwater in both solid (frozen) and liquid (water) form while the rest is saline sea water in the oceans. With a growing world population, higher energy demand and the effects of climate change, the demand for freshwater will spike against a limited supply. Moreover, as it becomes ever more important to cut greenhouse gas emissions, the role of freshwater in climate mitigation will come to the fore.

A serene natural landscape. Source(Emmanuel/iwaria)

Safe and clean water is a human right and is one of the sustainable development goals.

Freshwater itself is a natural resource that plays many roles in mitigation. The first is in nature based solutions like forests. Forests mitigate climate change because they absorb carbon dioxide in photosynthesis and also regulate atmospheric temperatures (heat) and moisture levels. They also buffer against climate impacts such as reducing the damage from flash floods etc.

Mitigation efforts concerning forests include afforestation and reforestation. The first is the growing of trees in new lands while the second is replanting trees in cleared but formerly forested areas. Both need considerable amounts of freshwater because water is one of the key ingredients for plant growth. These efforts cannot succeed without a good supply of water.

It is important to first verify the type of tree species planted in an area because different species have different water needs. Some types of trees are water intensive and require more water but maybe fast growing. Such trees place a demand on freshwater supply and increase competition with other domestic, industrial and ecosystem uses. Eucalyptus species for example have been known to dry up riverbeds. Notably, for climate mitigation, all tree species, including plantation forests, will absorb carbon dioxide but only the right mix of indigenous trees suited for a particular area will protect biodiversity, the freshwater supply and the larger ecosystem.

Lack of freshwater can cause trees in mature forests to actually release carbon dioxide as they start degrading and dying. This is the same for drying out grasslands and shrub lands. All ecosystems need water to maintain their functions and carbon stocks.

Droughts of which, climate change is a cause, impact forests by reducing growth rates of trees and their ability to sequester carbon.

Water is therefore essential for the climate mitigation function of forests and other natural vegetation groups.

Water is also needed for irrigation for croplands. Like all green vegetation, croplands sequester carbon both in the above ground parts (the trunk and all associated foliage) and below the ground (roots, tubers etc.). However, plant growth requires water. Irrigation is one of the adaptation responses to climate impacts in the agriculture sector, and works towards food security. Freshwater supply is needed in order to make this a reality.

An associated issue is soil carbon content whereby water plays a big part. Well drained soils and high soil moisture content is one of the requirements for high storage of soil carbon. Wet soils are able to lock in more carbon while dry soils release carbon into the atmosphere and are more prone to water and wind erosion. Soils hold a huge amount of carbon and are the second biggest carbon sinks after oceans.

Excess application of agrochemicals in the presence of water makes nitrogen fixing bacteria release nitrous oxide (N2O) into the atmosphere. N2O is a greenhouse gas.

In other ways, agroforestry practiced in farms can help increase freshwater flows by increasing the percolation rate of surface water and so increasing groundwater recharge. Trees shade the soil and reduce water loss from soils thus increasing their ability to lock in carbon. They hold soil together and prevent wind and water erosion and soil carbon loss. They also add to organic matter in soil by their biomass. Trees contribute to the hydrological cycle and improve the microclimate.

Fruit trees can be medicinal and also provide nutrition.

Water bodies are an important of climate mitigation in many ways. On their own, rivers and lakes naturally release small amounts of methane, which is a greenhouse gas. However, when agricultural chemicals such as nitrogen based fertilizers are washed into lakes and rivers, they fertilize the water body causing massive growth of plant and algae. This then rot to deplete dissolved oxygen in water and harm marine life while also releasing nitrous oxide, carbon dioxide and methane which are all greenhouse gases. In these way, these fresh water bodies become net sources of GHGS.

Peatlands and other wetlands are very carbon heavy, storing up carbon in their very rich organic soils which are usually waterlogged i.e. covered by water. This water is freshwater and in essence stops the complete breakdown of dead plant and animal organic matter. The waterlogged conditions (lack of oxygen) stop organic decomposition. Peatlands contain organic matter stored up for thousands of years (twice the amount of carbon in forests) though they only cover about 3% of global surface area. In order to conserve this carbon sequestering function, they need to be protected. Peatlands are usually drained or burnt for agriculture and mining which releases their vast stores of carbon. To protect them, they need to be rewetted (need water) and kept so. Peatlands also supply drinking water to communities.

Mangroves are coastal ecosystems that are dependent on constant inflow of freshwater from rivers. This is why they are located at river mouths in brackish water. The freshwater from rivers dilutes the salinity content of the water while increasing nutrient load. This allows for a delicate balance that allows mangroves to thrive. Mangroves absorb four times the amount of carbon dioxide terrestrial forests do.

The other types of coastal ecosystems i.e. seagrasses and saltmarshes also depend on freshwater flow to increase sediment and nutrient content in their habitats and enable them to thrive. These ecosystems are also strong absorbers of atmospheric carbon, locking it up in sediment, their bodies and the deep substrate beneath.

In terms of energy, hydropower is generated from dams and reservoirs built in river courses in order to generate electricity. These dams need a supply of freshwater as they are located across rivers. Hydropower necessitates the flooding of large areas next to a river. All the vegetation then covered by water releases methane as it rots. Not only so, but if the catchment area of such a river hence the dam is agricultural, then agrochemicals such as fertilizers and organic content will fill up the dam making it fertile and a source of both nitrous oxide and methane. The two are greenhouse gases. Large scale hydro alters water temperature i.e. dammed water is hotter than normal, and this also accelerates the rate of greenhouse emissions.

Unperturbed waterbodies (less human interference) act as carbon sinks instead of sources.

Freshwater is needed for negative emission technologies (NETS) such as growing of bio-energy crops with carbon capture and storage (BECCS). These crop types require land and compete with other land uses including agricultural crops. But most importantly they place quite a demand on freshwater supply because they have to be irrigated to grow. Therefore they interfere with the natural workings of an ecosystem and also alter the water cycle in such areas. BECCS act by absorbing atmospheric carbon dioxide emissions through photosynthesis and provide energy when they are burnt. They are carbon neutral or negative depending on where the resultant emissions are stored.

Carbon capture and storage (CCS), with CO2 injected into rock formations has the potential to infiltrate groundwater sources with the possibility of changing the characteristics of groundwater and its safety regarding consumption.

Freshwater is also needed to cool thermal power plants including nuclear and solar plants. The latter involves concentrated solar power (CSP) and solar PV to a very limited extent. Geothermal power might need reinjection of water into drilled wells to produce steam.

All these are climate mitigation strategies in the energy sector that require water.

Drinking water is another area concerning climate change mitigation. Freshwater from surface and ground sources is pumped or abstracted from one area, treated, transported and distributed using energy. Capacity to reduce emissions can be found in reducing losses through theft, leakage, poor metering, illegal connections and just wasteful use. Careful studying and mapping of entire water supply routes will yield information on the location of water losses, the time it happens, the cause and volumes. This will not only reduce costs for the water utility firm but it will also reduce energy used and therefore the emissions produced. Another solution is to use clean energy to cut emissions.

Wastewater is another major area concerning climate change mitigation. Basic and good sanitation is a human right, which unfortunately not everyone has access to. Sewage (wastewater) releases quite a significant amount of greenhouse gases (methane and nitrous oxide) apart from carbon dioxide which is released when energy (including electricity) is used in the entire chain (transport, airing, collection). They tally to around 3% of global emissions. Wastewater treatment plants (WWTPs) are a source of greenhouse gases especially methane because of the decomposition of organic matter. Moreover, untreated wastewater, of which a good portion of wastewater is released untreated into the environment on a global scale, is a big source of GHG emissions because of all the biological processes that happen in it.

When discharged into a water body in its raw state, wastewater immediately poisons the water making it unfit for human consumption of any kind and kills marine life. Not only so, it makes the said water body a net source of greenhouse gas emissions.

There is however huge potential for wastewater facilities because they can become a source of energy. The gases released (methane, nitrous oxide and biogas) can be collected and used to power the facility instead of using energy from the grid. If such a plant can in this manner be energy independent (supplying its own energy), then it is energy neutral. And in some instances it can actually supply more than it needs and sell this back to the main grid making it energy positive. This releases it from dependence on fossil fuel energy.

Another way to reduce emissions from these plants is to be more energy efficient. Reduce wastefulness.

Methane (CH4) can also be flared.

The biggest contributor to methane is faecal matter (human waste) which being broken down releases slightly less than three quarters of all CH4 emissions from WWTPs

Wastewater plants can benefit from the latest technology and better design in order to capture and reduce GHG emissions. They can also use renewables to supply energy making them “greener” and climate friendly.

Emissions from standalone septic tanks and sewers can be used to provide energy for household use reducing pressure on the use of fuelwood and other plant based sources of energy. This would work towards reducing of deforestation rates and forest degradation.

Independent sanitation solutions like pit latrines also release methane into the atmosphere and connecting them to sewerage facilities can help capture this greenhouse gas and put it to good use. However, they are a good solution to sanitation when constructed above ground water (to avoid contamination) and contribute to nutrient recycling. Such waste is organic and after proper handling and treatment can be used even in agriculture. This is what happens in composting toilets.

Concerning the Water, Sanitation and Health Sector (WASH) one of the problems that exist in relation to climate change mitigation is simply the lack of knowledge about the issue. Not much about this area makes it to climate discussions despite the potential.

Not only so, there is very little data that exists which would help in formulation of action plans.

Some of the solutions concerning freshwater and climate change mitigation is centralized and integrated governance. Climate change mitigation is not possible without use of freshwater to a large extent, and climate action impacts the water cycle and freshwater sources.

Therefore, solutions have to look at the issue holistically and not independent of one another.

Inclusion of the water sector in in Nationally Determined Contributions (NDCs) and national adaptation plans (NAPs) would be a step in the right direction.

Enhance cooperation between all players in the water sector. This includes all levels of government, regions, communities and users and especially in transboundary water resources.

Data gathering, monitoring and reporting is crucial if at all to measure the climate relevance of the water sector, especially sanitation. This translates to capacity building and training of manpower but also use of reliable technology.

Water is a common resource and there exists one global water cycle. Hence climate action concerning freshwater should take into account collective responsibility and unity in purpose.