Conclusion: Sustainable Freshwater Consumption

Throughout my blog posts, I have attempted to highlight how freshwater has been used in the past and present, and to explore the impacts of unsustainable freshwater consumption. 

Case studies such as the Aral Sea have shown how freshwater and related systems can be severely damaged, causing huge losses and consequences to both humans and the environment. I personally feel that human consumption of water in some parts of the world today, such as that of Las Vegas, is highly unsustainable which requires human intervention to not deplete already scarce resources beyond its limit. Furthermore, the human manipulation of freshwater systems through dams may have increased the surface area of freshwater but it has a significant influence on the freshwater system, as well as other ecosystems and their processes. Currently, the planet's consumption of freshwater has not passed the 'freshwater planetary boundary' limit, however, from what these previous case studies have shown, over-consumption has wider influences on other ecosystem functions and processes, hence using the 'quantity' freshwater consumption may not be adequate enough to show the impacts of unsustainable freshwater consumption. 

These blogs has reinforced my own understanding that the sustainable consumption for freshwater is not only important to ensure that there is a secure supply of freshwater for human consumption, but that without sustainable consumption, other ecosystem processes and functions will also be affected, which will in turn affect both the environment and humans alike. 

Freshwater Planetary Boundary

Throughout my blog, I have been commenting on how the human use of freshwater consumption has been highly unsustainable, but now I want to address whether humans have passed the global freshwater planetary boundary (PB). This blog will explore how the PB of freshwater was determined, and its limitations. 

What is the global freshwater planetary boundary?

The PB concept was defined by Rockstrom et al. (2009) and then was updated by Steffan et al. (2015) as the global safe operating limit of certain environmental processes that humans should not move beyond. They explain that within environmental systems, there are thresholds that are intrinsic to that environmental process, however the boundaries that was defined in their study was subjective to a set of human-determined values in defining a safe limit from a dangerous limit that would have adverse and undesirable effects on the system and humans alike (Figure 1).

Figure 1. Diagram of the Planetary Boundaries concept, showing safe zone, and zone of uncertainty about the ‘threshold’ [Rockstrom et al., 2009]. 

Global freshwater use is identified as one of the nine PB, and it is categorised as a ‘slow’ planetary process which has no defined threshold but it is a system that contributes to the resilience of Earth System processes when the changes in this system at local and regional scales are aggregated (Rockstrom et al., 2009). The study estimated a boundary of 4,000km³yr^-1 (uncertainty range of 4,000–6,000km³yr^-1) of the consumptive use of blue water (rivers, lakes, reservoirs and renewable groundwater), and when freshwater resources are consumed beyond this limit, both blue and green water-induced thresholds will be met such that global moisture feedbacks, biomass production, ecosystem functioning and carbon uptake by terrestrial systems are adversely affected. 90% of global green water and 20–50% blue water is required to sustain ecosystem services and aquatic ecosystem functions, respectively (Rockstrom et al., 2009). Steffan et al. (2015) uses the same boundary values, however the study updated the control variable that was used to define this threshold by including the hydrological characteristics of a river basin i.e. environmental flow requirements. This includes identifying the amount of water that can be withdrawn from rivers at the river basin-scale without adjusting the flow regime based on the river basins hydrological characteristics which would ensure an adequate ecosystem state.

Have we passed the global freshwater planetary boundary?

Our current consumption of freshwater is ~2,600lm³yr^-1 and given that the boundary is estimated at 4,000km³yr^-1, so surely, we are still within this safe operating space. Right?

However, on the one hand, an interesting study by Jaramillo & Destouni (2015) compares Destouni et al. (2013) and Steffan et al. (2015) estimates of global freshwater use with, and argues that Steffan et al. (2015) may have underestimated total freshwater consumption whereby we may have already passed the freshwater boundary. For example, reservoir-related freshwater consumption affect humidity and evapotranspiration up to 100km from the reservoir borders, thus having a larger impact on surrounding water resources such as higher evapotranspiration rates from raised groundwater levels (Destouni et al., 2013), which contrasts to Steffan et al. (2015) study whereby the evapotranspiration losses from raised groundwater levels is negated by a corresponding decrease of evapotranspiration rates in surface water downstream. Furthermore, evaporation rates in water storage or hydropower reservoirs have increased on average. Based on the net increase in basin-related and hydropower evapotranspiration losses in Switzerland alone, Destouni et al. (2013) found that global freshwater consumption increased to 1257km³, which is ~1000km³ higher than the amount identified by Steffan et al. (2015) (Figure 2). Jaramillo & Destouni (2015) does explain that there are limitations to Destouni et al. (2013) study given that evapotranspiration losses do not include other non-hydropower sources, and that evapotranspiration rates are generally lower due to Switzerland’s cooler climate, hence the total freshwater consumption of 3,569km³yr^-1 is a conservative figure. However, Destouni et al. (2013) provides a global synthesis, accounting for Et rates in all different types of water use across the globe and find that total freshwater use amounts to 4,664km³yr^-1 (Figure 2C), showing that we already surpassed Steffan et al. (2015) 4,000km³yr^-1 limit. 

Figure 2. Comparison of freshwater consumption by (A) Steffan et al. (2015); (B) Destouni et al. (2013) and (C) Destouni et al. (2013) & Shikomanov (1997); [Jaramillo & Destouni (2015)]

On the other hand, another study by Gerten et al. (2013) argues that Steffen et al. (2015) while accounting for environmental flow regimes have overestimated the limits to which blue-water can be consumed from freshwater resource. Gerten et al. (2013) argues that while using a bottom-up approach to quantify environmental flow regimes of local freshwater resources, the limit that they proposed (~2,800mk³yr^-1) is much lower than that proposed by Steffan et al. (2015) of 4,000km³yr^-1. They argue that Rockstrom et al. (2009) and Steffan et al. (2015) used a top-down approach which was based on global estimates of water availability and other processes, rather than including the spatiotemporal patterns of regional water resources.

Concluding Thoughts:

These studies show that defining a threshold for freshwater consumption is very complicated because there are many complex processes in the water cycle that have yet to be covered and thus making it difficult to assess the certainty the limit of how much freshwater we can consume. However, setting a limit to how much freshwater that can be consumed can be useful in helping to govern how much water is being used. However, the overconsumption of freshwater in specific regions can lead to other impacts such as biodiversity loss or increased salt and chemical deposition (e.g. Aral Sea case study blog). Hence, it is important to address the unsustainable overconsumption of freshwater resources with other PB thresholds. 

Freshwater Quality and Pollution

The quantity of global freshwater resources has been changing over time and human activity has been one of the largest drivers in this change. The sustainable use of freshwater resources has been one of the main themes that I have been exploring throughout my blogs in terms of ‘quantity’. However, another aspect of sustainable use can also include the ‘quality’ of freshwater resources, since polluted freshwater resources can limit the extent to which this resource can be consumed. In this blog, I will explore how agriculture, industry and urban waste impacts the quality of freshwater resources.

Freshwater resources and ecosystems are becoming more easily polluted, whereby waste from multiple sources (agricultural fertilisers, industrial chemicals, and urban/human untreated waste) are being deposited into freshwater systems, and are ultimately polluting these resources beyond natural levels (Zamparas & Zacharias, 2014). Eutrophication is a large concern in many freshwater ecosystems due to the increased deposition of phosphorous (P) and nitrogen (N) fertilisers and other polluting chemicals from both point and non-point sources.

Non-point sources include the global consumption of fertilisers in agriculture, and the poor management of fertiliser application increases the losses of these nutrients from the soil through surface runoff processes; 20% of nitrogen fertilisers is lost through surface runoff and leaching (Khan & Mohammad, 2014). The nutrient enrichment of freshwater bodies occurs where algal blooms develop over the surface of the water which results in a huge decline in the quality of the water, inducing a state of hypoxia – hypoxia occurs when dissolved oxygen levels fall below 2ml of O₂/litre, making it difficult for oxygen dependent plants and organisms to live in (Diaz & Rosenburg, 2008). An interesting study by Withers et al. (2014) explains that there is a delay during which the effects of applying inorganic fertilisers will appear. For example, in the UK the intense application of N and P fertilisers was encouraged during post-World War II period to produce more food for the nation. However, these nutrients were stored temporarily or permanently in the soil until runoff or leaching into groundwater resources occurred, and this left behind a ‘legacy’ of background leakage of nutrients in UK inland waters. Thus, nitrogen levels appear to be increasing across UK lowland aquifers, despite lower levels of nitrogen fertilisers being used today and the stores of fertilisers in the soil and groundwater provides sources of nutrients during periods have no runoff or leaching due to low rainfall (Howden et al., 2011). Hence, freshwater resources in the UK are expected to experience long-term declines in water quality from both historical and current uses of fertilisers.

Point sources include wastewater from industrial and treatment plants, whereby pathogenic organisms, inorganic and toxic chemicals contaminate local freshwater systems and environments. For example, Lake Geneva in Switzerland supplies water to 70,000 people, however Vida Bay in Lake Geneva is one of the most contaminated areas of the Lake due to wastewater contamination (Thevenon & Poté, 2012). In this study, Thevenon & Poté (2012) uses sediment cores to reconstruct the polluting elements over a decadal timescale from 1200 to present (Figure 1). The record shows that from 1900, trace metal elements have increased significantly, compared to the steady levels between 1200-1800 such as lead (Pb) from 20-30mg/g to 60mg/g from 1600 to 1960. The sediment record at Vida Bay (Figure 2) shows an increase in caesium (¹³⁷Cs) at ~45cm of the sediment record which coincides with the construction of the outlet pipe of the wastewater treatment plant in 1964 at Vida Bay (Thevenon & Poté, 2012). Hence, the discharge of treated industrial/domestic wastewater results in further contamination of the environment and aquatic ecosystems. Furthermore, the surface sediments which contains high organic matter contents (e.g. P and N) reflects faecal indicator bacteria, Escherichia coli – in 2007, high concentrations of E.coli of 10⁴-10⁶ CFU/g was located around the Vida Bay outlet pipe and 10⁵-10⁷ around Chamberone River compared to 1996 where levels were non-existent. Such increases in trace metals and faecal bacteria in Vida Bay will have adverse effects on human health due to contamination of drinking water; this case study highlights the significant role industries have on freshwater contamination in addition to the agricultural use of fertilisers.

Figure 1. Sedimentary trace elements from centre part of Lake Geneva (Thevenon & Poté, 2012)

Figure 2. Sediment record from Vida Bay in Lake Geneva (Thevenon & Poté, 2012)

Freshwater resources are also being polluted due to the poor management of wastewater in urban areas, and predominantly in rapidly urbanising cities that are unable to implement adequate sewerage and treatment facilities. For example, the per capita pollution load of urban discharge into the Bagmati River, Kathmandu Valley in Nepal is estimated at 31gBOD/capita/day (Kam & Harada, 2001). Biochemical Oxygen Demand (BOD) increased from 3.8 to 30mg/litre from 1995 to 1998, and faecal coliform increased from 1.0x10⁴ to 8.75x10³MPN/100ml in the same period. In Dhaka, BOD and faecal coliform levels are within 20-30mg/litre and 10⁴-10⁵MNP/100 range, but the environmental standards for safe drinking water are less than 3mg/litre for BOD and 5000MPN/100ml (Kam & Harada, 2001). Current levels in Dhaka exceeds the safe human consumption limit due to pollutants from various urban sources (domestic wastewater) which are being discharged unsafely into rivers and local water sources. 

Concluding Thoughts:

Freshwater resources and ecosystems are subjected to huge declines in water quality as a result of human activities, ranging from agriculture, industrial activity and urban living spaces. In addition to the over-consumption of freshwater resources, the degradation of freshwater quality can equally diminish the amount of freshwater available to us for human use. Overall, managing both the quality and quantity of freshwater resources are important in achieving water security, especially in a warming world where water resources are becoming more scarce. The application of fertilisers should be timed so as to avoid heavy rainfall periods, industrial wastewater should be better managed before discharging into the environment and urban wastewater and sewage systems should be at the forefront of urban policies. Freshwater quality can be easily maintained but will require human intervention and better management.

The role of dams and reservoirs in the consumption of freshwater

IPCC AR5 report suggests that under climate change, surface freshwater resources will likely decline due to the increased variability in rainfall, river flow and snow melt and ice storage (Cisneros et al., 2014). Areas near the Mediterranean, Southern Africa and East Asia will likely experience lower rainfall and higher temperatures and thus some areas will become more water-stressed, and population growth and urbanisation will only add to this water stress. One adaptive method to climate change impacts is the construction of dams and reservoirs. Watts et al. (2011) strongly argues that dam construction can reduce the effects of climate change while increasing the resilience of water systems and contributing to ecosystem restoration. In this blog, I am going to explore the role of dams in addressing the needs of water stress areas, the benefits and the downfalls of dam construction.

Dams have multiple uses ranging from hydropower, inland navigation, flood control, water supply for domestic and industrial use, and water supply for irrigation. These uses can be highly beneficial for those most vulnerable to changes in e.g. rainfall. 94% and 66% of agriculture is rain-fed in sub-Saharan Africa and Asia, respectively, thus these populations are highly vulnerable to climate change (McCartney and Smakhtin, 2010). In Africa, climate change is predicted to increase droughts and rainfall will become more intense and concentrated within the space of a few months which results in floods and large runoffs (IPCC, 2007). Ideally dams can bridge the gap between rainfall variability and supply, as well as reducing the impacts of intense runoffs and floods (ICID). However, the construction of dams in these vulnerable areas may not be able to derive any benefits from it. For example, the Kariba Dam in Zambia was declared to be in “dire” condition as a result of droughts, which are intensified by climate change (Leslie, the NewYorker).

Throughout my blogs, I have been arguing how human consumption of freshwater have been unsustainable to the extent where water resources are declining across the globe, however a study by Pekel et al. (2016) presents an alternative viewpoint, suggesting that surface freshwater resources are in fact increasing. Pekel et al. (2016) explains that globally, surface water resources have permanently declined in areas such as the Middle East and Central Asia as a result of human activities and overconsumption, however there has been an increase in surface water elsewhere which is mainly through dams and reservoir filling. They found that 90,000km² of surface water has been permanently lost, however 184,000km² of permanent water has formed in areas that previously had no water and Asia gained the largest amount of permanent water of 71,000km² since 1984. In terms of quantifying freshwater resources, this study has shown that we have not lost a significant amount of freshwater, but instead we have gained almost double of what we lost. However, this does not identify whether the use of dams is sustainable; what are the impacts of dams on a hydrological regime and the local environment?

The Three Gorges Dam (TGD) is located in the Yangtze river basin and is one of the world’s largest dam with a 600km long reservoir and 4000km² storage capacity (Gleick, 2013). This dam has large benefits such as having a large storage capacity and thus an extensive water supply during periods of long drought, and reducing major flooding downstream of the Yangtze basin (Sun et al., 2012). However, there are significant concerns to the environment, and people’s health and livelihoods. For example, sediment retention can significantly damage downstream environments. Jingjiang River and Dongting Lake usually received sediments before the TDG was built, but now it supplies the Yangtze river with sediments due to the retention of sediments at the TDG (Sun et al., 2012). The decreased sediment loads can cause suffocation and abrasions to biota and habitats in the surrounding environment. Moreover, the alteration of the hydrological regime has huge implications on wetlands and lakes whereby the storage of water during the autumn period and release during winter and spring resulted in the decline of water levels in the Lake Dongting wetland. Water levels decreased by 2.11m with an extreme value of 3.02m in 2009 since the dam’s construction (Sun et al., 2012). Other environmental problems include eutrophication, algal blooms, the decline of certain fish species, and the erosion of downstream riverbeds (Xu et al., 2013). The water quality in 38 small tributaries had declined since 2003 from 14-29% by 2008 depending on the portion of the river and the frequency of algal bloom events increased from 3 to 26 between 2003 to 2010 (Xu et al., 2013). By 2008, approximately 1.13 million people were displaced and resettled to areas near the reservoir or in urban cities, however the resettlement of these populations did not consider the environmental carrying capacity of these populations thus having wider implications on local resources (Xu et al., 2013).

Concluding Thoughts:

The overconsumption and pollution of freshwater resources, and climate change largely influences water availability in many areas of the world, and so the use of dams can prove to be a solution to addressing water security issues. Storing water can provide for a constant supply of water and especially during periods of drought, thereby reducing water scarcity. The study by Pekel et al. (2016) explains that surface water supplies has increased as a result of dams and reservoirs, however, case studies such as the TDG shows that dams and reservoirs have wider implications to the local environment, water quality and populations living near water resources, such as the water level decline of Lake Dongting in the Yangtze river basin, or the decline in water quality. Thus, this should only raise concerns regarding the sustainability of using dams in addressing water scarcity issues and if we should use dams as a permanent solution for guaranteeing a constant supply of freshwater. 

Freshwater Use in Las Vegas

When I mention ‘Las Vegas’, what comes to mind? What comes to my mind are impressive displays of fountains and magical bursts of water in a city that was built in an arid desert, but I also think that it is such a waste of water. 

 

 

Personally, I cannot put it any better than Tim Barnett (ScrippsInstitution of Oceanography): “It’s just going to be screwed. And relatively quickly. Unless it can find a way to get more water from somewhere Las Vegas is out of business. Yet they’re still building, which is stupid”.
In this blog, I want to explore where Las Vegas derives their water sources, how much water is used, and the impacts on these water sources.

Las Vegas City has a population of more than 600,000, but the Las Vegas metropolitan area accounts for more than 2 million people, and the population size is projected to increase to more than 3 million by 2042 (World Population Review, 2016). The large increase in population for the metropolitan area results in large demand and pressure for more water resources in an arid environment, thus misbalancing the demand and supply of water that the catchment can provide (Salvaggio et al., 2013). 

The Southern Nevada Water Authority (SNWA) derives their water sources from the Colorado river which flows into the Lake Mead reservoir behind Hoover dam, providing 90% of the water to the metropolitan area, however the Colorado river flows are declining due to droughts and climate change which is proving to be a huge challenge for water resource management with an increasing population and an expansion in the urban area (Salviaggio et al., 2012). Because of the decline in river flows, Lake Mead reservoir water levels has fallen to an all-time low of 1080 feet above sea level in the last 78 years (Icenhower and Dhar, 2015). Las Vegas uses up to 219 gallons of water per person per day and experiences an annual average of less than 13cm of rainfall (Dawadi & Ahmad, 2013). Hence, the combination of low rainfall levels, declining water levels, drought and climate change and an increasing population requires serious management and conservation plans if Las Vegas would hope to reduce the threats to their water security in the near future.

SNWA decided to build a third intake pipeline as a precaution to declining lake levels so that water can still be supplied to the city even if Lake Mead continues to decline to its lowest-record water levels (Locher, 2015). This does not appear to be a sustainable method to address the water decline, but rather a back-up plan which attempts to delay serious environmental concerns whereby the continued consumption of water from Lake Mead will eventually drain the entire reservoir. Furthermore, a $650 million pumping station will be built by 2020 to reach and draw water from the deepest depths of Lake Mead as an alternative water source to the declining Colorado river flows. Interestingly, declining river flows and lake levels should be a clear sign that the management of water resources in this catchment and its regeneration should be the number one priority. But instead, the SNWA committee and board chairwoman Mary Beth Scow insists that further pumps and pipes will need to be built to ensure a constant water supply to the city to further support the strong Nevadan economy (Walton, 2014). Castle et al. (2014) notes that while increasing demand would be placed on groundwater reservoirs in the Colorado River basin, these groundwater sources will not be able to meet future water demands and thus the long-term security of water will be significantly threatened.

Clearly, supply-side management policies can insofar provide a sustainable level of water supply into the city and so alternative methods. Dawadi & Ahmad (2013) suggests that a combination of water conservation and better pricing policies will enable water supplies to last longer into the near future. This study modelled conservation and policy scenarios to determine which methods would reduce demand for water. They found that both indoor-outdoor conservation practices such as managing water appliances (indoor) and converting turn grass into desert landscape (outdoor), and a price rise of water consumption by 50% had reduced water demand by 35% for 2035. These results are ideal for water conservation, but given that they are only model predictions, it may not translate very easily into management plans and practice. Indoor and outdoor conservation can be easily adopted whereas people may not agree or be willing to pay more for their water. Although, Salvaggio (2013) found that when people are knowledgeable about drought conditions and value the environment, then they are more supportive of water price increases.

Concluding thoughts:

Personally, I feel that a city like Las Vegas should not exist due to the impractical demands for water in a desert, which I believe to be a wasteful and unnecessary allocation of water resources. However, given that it still exists and it is unlikely that the city will be demolished just to conserve water, management policies and conservation is crucial for the future water security of the city and its inhabitants. Both demand and supply side policies should be considered so that the sustainability of water use can be fully maximised.

I would like to highlight an article by Jennifer Robinson in the Las Vegas Review-Journal (2015), who interestingly believes that there is no water crisis in Las Vegas because the city already has an effective management strategy in place, and so encourages the growth and expansion of the city. In contrast, the former general manager of the Southern Nevada Water Authority (in the video below) explains that Las Vegas is indeed facing a crisis and that the impacts of climate change can worsen this crisis. I implore you to read the article and watch the video, and determine for yourself if Las Vegas is using water sustainably and if Las Vegas can continue to expand economically and in population size with regards to water supply. 

Sustainable or Not?

The establishment of Las Vegas is one that always shocks me because it is a city that thrives and strives in the desert where drought is prevalent. Where does it get its water from? How much water does it use? Why does Las Vegas need that many fountains? My next blog will look at freshwater use from the Colorado River and Las Vegas and I will question its sustainability. For now, see the video below for a brief introduction to water use and Las Vegas. 

Shrinking Freshwater Resources: Part II

Not only is freshwater resources from surface supplies are vulnerable to being overused and depleted, groundwater resources are equally vulnerable and are being increasingly used in many areas of the world and to the point of depletion. Groundwater depletion can be defined as the rate of natural recharge to the aquifer being less than the rate of abstraction and discharge (Wada et al., 2010). Wada et al. (2010) study explains that areas prone to high levels of groundwater abstraction include North-East Pakistan, North-West India, North-East China, the central valley of California, and central US to name a few. They found that total global groundwater depletion totalled to 39% of the total yearly groundwater abstraction, which is an alarming rate for our global resources to be depleted.

Causes for groundwater depletion is a result of the overexploitation of these resources for agricultural, domestic, and industrial purposes. For example, areas in the world which has little access or supply to surface freshwater resources use groundwater systems as an alternative. Climate change is expected to have a huge impact on rainfall patterns over Africa, causing some areas to experience more droughts and others more flooding. Africa highly depends on rainfall and surface water sources and with this core supply reducing, alternative sources like groundwater is expected to be further relied upon for agricultural, domestic and industrial use as an adaptive method to climate change (Taylor et al., 2009). However, MacDonald et al. (2012) has found that there is a limit to how much groundwater resources can be used to supply populations in Africa. The study found that for low intense use, a groundwater borehole must be able to provide >0.1 l s^-1 whereas urban populations or large commercial scale irrigation schemes will require at least 5 l s^-1. Hence it is important to recognise that while populations use groundwater resources as an alternative resource, it may not be sufficient to keep up with the increasing demand for freshwater resources e.g. from an increase in population in Africa, ultimately leading to the depletion of groundwater resources.
In countries like the United States, local groundwater supplies are depleted for hydraulic fracturing to recover fossil fuels. Hydraulic fracking requires large amounts of water, and in a period where demand for energy is high, alternative solutions like fracking are adopted to fulfil that energy need. And thus, groundwater resources are highly affected. Water used for hydraulic fracturing increased from 10 to 55 million gallons of water in Michigan (Burton Jr er al., 2014). Michigan is considered to have an abundant amount of groundwater resources, but the demand and need for energy will only push for hydraulic fracturing processes in other areas, and thus the groundwater resources in those areas are likely to be highly impacted too.
India is the world largest user of groundwater resources, but these resources are reaching unsustainable limits (World Bank, 2010). India is endowed with an abundance of groundwater resources but the depletion of this resource can be linked back to the green revolution. Surface water was highly used by many populations across India, however since it was not accessible, groundwater was used more extensively for agriculture and drinking purposes. 85% of drinking water in rural areas comes from groundwater supplies, and increasingly populated urban areas such as Delhi consumes almost 50% of groundwater (World Bank, 2010).

Impacts of groundwater depletion has wider implications and it includes not only the depletion of freshwater resources, but the quality of water will decrease as wells are being dug for more water, land subsidence will occur, streamflow depletion and the increased chances of sea water intrusion in coastal aquifers (Famigeltti, 2014). Hence the environment tends to suffer the consequences of this groundwater depletion. For example, a case study in the North China Plain exhibits these same consequences on the environment as well whereby cones of depressions have formed largely under the urban prefectures of Cangzhou and Hengshui, declining at a rate of 1.0 and 1.7 m/year (Changming et al., 2001). Also, land subsidence in the Xingang area of Tianjin affected the strength of the harbour structures and increased the vulnerability of this region to storms.
Coastal cities that relies on groundwater resources is at the risk of seawater intrusion and a great decline in the quality of drinking water. For example, a study by (Mtoni et al., 2012) has shown that in the city of Dar es Salam, Tanzania, shallow wells are dominated by sodium, calcium and chloride ions due to increasing seawater intrusion near boreholes located in the coast. Deeper aquifers are still more mineralised, but if the rate of groundwater overexploitation continues unsustainably, then these deeper aquifers are likely to deteriorate in quality as well.

Groundwater resources are just as important as surface water sources, and once over exploited to an unsustainable limit, it can be difficult to bring these resources back to its previous level and quality. The management of freshwater resources is highly important for human wellbeing, and agricultural, domestic and industrial use, although freshwater systems are generally isolated on regional scales and so regional scale management is required. Thus I would like to further explore how freshwater resources are currently being used and if it is managed properly, sustainable and without excess consumption of it.