A Critical Evaluation of the Impacts of Global Warming and Climate Change on Water Resources. A Literature Review

Kennedy W.Nyongesa1and Francis O. Obiria2

1Institute of Climate Change and Adaptation, University of Nairobi 2 Kisii University


Water resources are important to both society and ecosystems. They constitute one of its vital assets that significantly contribute to the socio-economic development and poverty eradication. Water is an indispensible element of life. We depend on a reliable, clean supply of drinking water to sustain our health. We also need water for agriculture, energy production, navigation, recreation, and manufacturing. The major source of water for these resources is direct rainfall, which is recently experiencing variability attributed to climate change that has threatened the distribution of resources and water availability around the globe. From the available literature based on the declining water resources management, the paper prompts to answer questions such as; what are the impacts of climate change and global warming on water resources around the globe? How is climate change and global warming manifested? What climate change related challenges face the water resource management of Lake Victoria water catchment basin in Kenya? The paper shows  that the variability in climate is affecting the water resources at a faster rate, owing to pressure also on them which exacerbate the situation. Climate change manifestations in form of droughts, high temperatures, and reduced or increased run-offs have had and continue to have an impact on the quantity, variability, timing, form, and intensity of precipitation, including water quality impairment, and salt water intrusion to coastal water supplies. These have affected many sectors, including energy production, infrastructure, human health, agriculture, and ecosystems. This paper suggests how we need to confront the climate change-related challenges on water resources through adopting a variety of adaptation practices, and developing alternative strategies for water management.

Key words: Climate change, Global warming, Water resources, Challenges, Impacts

Introduction and Background

Water is an indispensible element of life. Water resources are closely related to climate and highly sensitive to climate variability and change as asserted by Nováky (1999). Climate change is a phenomenon we can no longer deny as its effects have become increasingly evident worldwide. Water occurs on earth in many various forms as rivers, lakes, ground water, or soil moisture. Water resources depend strongly on climate and available water resources vary from region to another in relation to spatial variation in climate. Climatic manifestations in form of precipitation and temperature determine the hydrological processes and thus the hydrological characteristics of water resources such as water level or discharge of rivers, water amount in soil which varies with time.

As the earth’s temperature continues to rise, we can expect a significant impact on our fresh water supplies with the potential for devastating effects on these resources (Grace Communication Foundation, 2016). Climate change is thus creating major consequences for water resources through its impacts on the planet’s hydrology. Hydrology, a physical science, encompasses the distribution, movement, and quality of water in the Earth system (Yarnal, 2014). Water resources, a social science, covers the use of water by humans through agricultural, industrial, domestic, recreational, and other activities. Hence, by altering water’s distribution, movement, and quality, climate change is causing humans to adjust the ways they use water.

As temperatures increase, evaporation increases, sometimes resulting in droughts; yet people and animals need more water to maintain their health and thrive. Many important economic activities, like producing energy at power plants, raising livestock, and growing food crops, also require water (EPA, 2015). The amount of water available for these activities may be reduced as the Earth warms, and if competition for water resources increases.

It is on this background therefore, that it is evident that climate change has and is expected to impact on the sources of water and water availability and thus, imperative to evaluate the impacts climate change is likely to pose on water resources globally. The paper specifically identifies the climate change and global warming manifestations, delineates the impacts of climate change and global warming on water resources, and investigates the climate change related challenges on the management of water resources in the Lake Victoria Basin water catchment area of Kenya.

Manifestations of climate change and global warming

A change in climate is attributed directly or indirectly to human activity in addition to natural climate variability that alters the composition of the global atmosphere which is observed over comparable time periods. Climate change therefore, is described as a change in the statistical distribution of weather patterns when that change lasts for an extended period of time ( decades to millions of years). According to Little and Garruto (2007), climate change manifested as  global warming results from increased production of greenhouse gases, such as carbon dioxide, thus leading to a net heat gain at the surface of the earth. In other words, the earth is heating up, and there are both predictable and unpredictable consequences of this thermal imbalance, especially on water resources.

Water resources, a social science, covers the use of water by humans through agricultural, industrial, domestic, recreational, and other activities. At the global scale, there is evidence of a broadly coherent pattern of change in annual runoff, with some regions experiencing an increase (IPCC, 2008; Tao et al., 2003; Hyvarinen, 2003,; Walter et al., 2004), particularly at higher latitudes, and others a decrease, for example in parts of West Africa, southern Europe and southern Latin America (IPCC, 2008; Milly et al., 2005).

According to Barnett et al. (2004), the clearest change indicated by the climate-change simulations is a general large-scale warming: a warming projected that by the middle of the century to reach an additional 1–2 ◦C as compared to present. And the most significant impact of this warming would be a large reduction in mountain snowpack and a commensurate reduction in natural water storage. And for that matter, current demands on water resources in many parts of the world will not be met under plausible future climate conditions, much less the demands of a larger population and a larger economy.

With global warming climate change manifesting in reduced precipitations due to shifts in weather patterns, the water resources presupposed beneficial allocation is bound to be at a brink of failure to their mandate (Barnett, et al., 2004). And with less fresh water available, the water resources around the globe could experience a dramatic increase in salinity and subsequent ecosystem disruption.

Impacts of climate change and global warming on water resources on global scale

A climate-related warming of lakes and rivers has been observed over recent decades. According to IPCC (2008), hydrological changes as a result of climate change and/or global warming may have impacts that are positive in some aspects and negative in others. For example, increased annual runoff may produce benefits for a variety of both in-stream and out-of-stream water users by increasing renewable water resources, but may simultaneously generate harm by increasing flood risk. Also due to warming, many lakes exhibit prolonged stratification with decreases in surface layer nutrient concentration, and prolonged depletion of oxygen in deeper layers, and while some lake levels have risen in Mongolia and China (Xinjiang) in response to increased snow- and ice melt, other lake levels in China (Qinghai), Australia, Africa (Zimbabwe, Zambia and Malawi), North America (North Dakota) and Europe (central Italy) have declined due to the combined effects of drought, warming and human activities (IPCC, 2008).

The effects of global warming are already being seen around the globe in terms of earlier melting of mountain snow packs and earlier dates for spring runoff (Barnett et al., 2004; Dettinger et al., 2004; Stewart et al., 2004). And for that matter, current demands on water resources in many parts of the world will not be met under plausible future climate conditions, much less the demands of a larger population and a larger economy. With global warming climate change manifesting in reduced precipitations due to shifts in weather patterns, the water resources presupposed beneficial allocation is bound to be at a brink of failure to their mandate. With less fresh water available, the water resources around the globe could experience a dramatic increase in salinity and subsequent ecosystem disruption (Barnett et al., 2004). The following climate change and/or global warming impacts are posed on the water resources around the globe;

Despite predictions of increased precipitation in most regions around the globe, net decreases in water availability are expected in those areas, due to offsetting increases in evaporation (Adam and Peck, 2008). Warmer temperatures increase the rate of evaporation of water into the atmosphere, in effect increasing the atmosphere’s capacity to “hold” water.Increased evaporation may dry out some areas and fall as excess precipitation on other areas (EPA, 2015). 

Changes in the amount of rain falling during storms provide evidence that the water cycle is already changing. Over the past 50 years, the amount of rain falling during the most intense 1% of storms increased by almost 20%.Warming winter temperatures cause more precipitation to fall as rain rather than snow. Furthermore, rising temperatures cause snow to begin melting earlier in the year. This alters the timing of stream flow in rivers that have their sources in mountainous areas (EPA, 2015). Many areas around the globe, especially those of Africa, currently face water supply issues. The amount of water available in these areas is already limited, and demand will continue to rise as population grows. Figure1 shows the the Conceptual framework as envisaged in this review.

Climate change is expected to affect water quality in both inland and coastal areas. Specifically, precipitation is expected to occur more frequently via high-intensity rainfall events, causing increased runoff and erosion (Adams and Peck, 2008). More sediments and chemical runoff will therefore be transported into streams and groundwater systems, impairing water quality. Water quality may be further impaired if decreases in water supply cause nutrients and contaminants to become more concentrated. Adams and Peck (2008) further that, rising air and water temperatures which are manifestations of climate change or global warming will also impact water quality by increasing primary production, organic matter decomposition, and nutrient cycling rates in lakes and streams, resulting in lower dissolved oxygen levels. And for that case, lakes and wetlands associated with return flows from irrigated agriculture are of particular concern. This suite of water quality effects will increase the number of water bodies in violation of today’s water quality standards, worsen the quality of water bodies that are currently in violation, and ultimately increase the cost of meeting current water quality goals for both consumptive and environmental purposes (Adams and Peck, 2008).

The quality of water supply in coastal and island regions is at risk from rising sea level and changes in precipitation. Rising sea level and the occurrence of drought can increase the salinity of both surface water and ground water through salt water intrusion (EPA, 2015). Furthermore, water quality could suffer in areas experiencing increases in rainfall. For example, in United States of America in the Northeast and Midwest increases in heavy precipitation events could cause problems for the water infrastructure, as sewer systems and water treatment plants are overwhelmed by the increased volumes of water (EPA, 2015).Heavy downpours can increase the amount of runoff into rivers and lakes, washing sediment, nutrients, pollutants, trash, animal waste, and other materials into water supplies, making them unusable, unsafe, or in need of water treatment. In addition, as more freshwater is removed from rivers for human use, saltwater will move farther upstream. Drought can cause coastal water resources to become more saline as freshwater supplies from rivers are reduced.

Increased evaporation rates as a result of higher temperatures are expected to reduce water supplies in many regions of the world. According to Adam and Peck (2008), the greatest deficits are expected to occur in the summer, leading to decreased soil moisture levels and more frequent and severe agricultural drought. More frequent and severe droughts arising from climate change bound to have serious management implications for water resource users.

The greatest effects of climate change are also projected to manifest on water resources linked to hydro-electric generation as most regions of the globe which demand on water to produce energy through hydropower have been earmarked to be impeded with the manifestations of climate change and global warming especially droughts which reduce the water levels. This conforms to EPA (2015) study that if climate change results in lower stream-flows in areas where hydropower is generated, it will reduce the amount of energy that can be produced, for example, according to Barnett et al. (2004),  users of Colorado River hydroelectric power will be affected by lower reservoir levels and flows, which will result in reductions in hydropower generation by as much as 40%. Changes in the timing of stream-flow can also have an impact on the ability to produce hydroelectricity.

Climate change impacts on water resources according to EPA (2015) also affect tourism and recreation. The quality of lakes, streams, coastal beaches, and other water bodies that are used for swimming, fishing, and other recreational activities can be affected by changes in precipitation, increases in temperature, and sea level rise.

Many rivers, which are important sources of water for irrigated agriculture, are bound to affect such activities. According to Barnett, et al. (2004), with less runoff, it will mean reduced ability to meet irrigation needs, higher water temperatures, and increased conflict between agricultural users and those whose principal concern is sustaining endangered fish populations. Higher temperatures and increased variability of precipitation would in general, lead to increased irrigation water demand, even if the total precipitation during the growing season remains the same. The impact of climate change on optimal growing periods, and on yield-maximizing irrigation water use, has been modeled assuming no change in either irrigated area and/or climate variability (IPCC, 2008).

Increased temperature also affects in-lake chemical processes. According to IPCC (2008), there have been decreases in dissolved inorganic nitrogen from greater phytoplankton productivity and greater in-lake alkalinity generation and increases in pH in soft-water lakes. Decreased solubility from higher temperatures significantly contribute to decrease in aluminum concentration (IPCC, 2008; Vesely et al., 2003), whereas lakes with warmer water temperatures have increased mercury methylation and higher mercury levels in fish (IPCC, 2008; Bodaly et al., 1993). Aquatic species that live in only cold water environments, such as salmon, will be affected by rising water temperatures (EPA, 2015). This is attributed to the changing water temperatures that are poised to affect the geographic range of fish species.

A variety of climatic processes have influenced flood processes around the world, resulting in river floods, flash floods, urban floods, sewer floods, glacial lake outburst floods  and coastal floods (IPCC, 2008). The observed increase in precipitation intensity and other observed climate changes, for instance, an increase in westerly weather patterns during winter over Europe, leading to very rainy low-pressure systems that often trigger floods (IPCC, 2008; Kron and Berz, 2007), indicate that climate change might already have had an impact on the intensity and frequency of floods.

Global warming manifestation in form of drought is bound to as well affect the water resources. The term drought according to IPCC (2008) refers to a meteorological drought (precipitation well below average), hydrological drought (low river flows and low water levels in rivers, lakes and groundwater), agricultural drought (low soil moisture), and environmental drought (a combination of the above).  Due to excessive water withdrawals as a result of climate change which enhance evaporation due to decreased run-offs and increased temperatures, this has exacerbated the impact of drought in more regions of the world. Droughts have become more common, especially in the tropics and sub-tropics, since the 1970s (IPCC, 2008). For instance, in Australia and Europe, direct links to global warming have been inferred through the extreme nature of high temperatures and heat waves accompanying recent droughts.

Droughts affect rain-fed agricultural production as well as water supply for domestic, industrial and agricultural purposes. IPCC (2008) further states that the 2003 heat wave in Europe, which was attributable to global warming accompanied by annual precipitation deficits up to 300 mm contributed to the estimated 30% reduction in gross primary production of terrestrial ecosystems over Europe. That is, many major rivers were at record low levels, resulting in disruption of inland navigation, irrigation and power plant cooling.

Higher water temperatures have been reported in lakes in response to warmer conditions, thus altering the lake physics. Since the 1960s, surface water temperatures have warmed by between 0.2 and 2.0°C in lakes and rivers in Europe, North America and Asia. Along with warming surface waters, deep-water temperatures (which reflect long term trends) of the large East African lakes (Edward, Albert, Kivu, Victoria, Tanganyika and Malawi) have warmed by between 0.2 and 0.7°C since the early 1900s (IPCC, 2008). This increased water temperature and longer ice-free seasons influence the thermal stratification and internal hydrodynamics of lakes. In warmer years, surface water temperatures are higher, evaporative water loss increases, summer stratification occurs earlier in the season, and thermo clines become shallower. Increased stratification reduces water movement across the thermo cline, inhibiting the upwelling and mixing that provides essential nutrients to the food web.

Climate change related challenges in the management of water resources in the Lake Victoria water catchment basin in Kenya

According to Inter-governmental Panel on Climate Change, climate change and variability have the potential to impact negatively on water availability, and access to and demand for water in most countries, particularly in Africa. Climate change is expected to alter and hence bring changes to the hydrological cycle, temperature balance and rainfall pattern (Mwiturubani, 2009).

Recent climate changes and global warming manifested in droughts, reductions in precipitation, and warmer, drier seasons have caused water supplies in Lake Victoria water catchment basin to decrease. There are also several issues and challenges surrounding water resources of the Lake Victoria water catchment area of Kenya in particular, which are aggravated by climate change and variability and population growth among others. The current water management practices in Kenya and its immediate shareholders of the water catchment of Lake Victoria may not be robust to cope with these challenges which impact on water resources and increase water use requirements since increasing and per capita availability of water resources is reducing day by day (Nsubuga, et al., 2014).

From a hydrological perspective, Lake Victoria, the largest water resource exerts a big influence in Kenya’s and East Africa’s climate. The main source of water for the lake is rain, but due to rainfall anomalies, the lake has consequently displayed large and rapid changes; that there is a significant correlation between lake rainfall series and lake levels indicating that the lake is sensitive to climate change (Nsubuga, 2014).

The frequent recurrence of extreme weather events (floods and droughts) and increasingly erratic rainfall are a big challenge to the management of water resources (Nsubuga, 2014). The variability in seasonal rainfall, has significantly affected the different socio-economic activities that are heavily dependent on rainfall ad thus, resort to depending on the available water sources which also face the similar trend of challenge of climate change and/or global warming. It is therefore, evident that climate change is expected to impact on rainfall which is a major source of lake/river water, thus pose challenges on the management of water resources of Lake Victoria water catchment basin of Kenya.

Despite the water demand of Lake Victoria being high and its supply also being phenomenal in serving over 180 million people in East and Central Africa, it faces a challenge of climate change in terms of management of its water resources. Climate change poses a conceptual challenge to water managers by introducing uncertainty in future hydrological conditions. Water management in the face of climate change has not adopted a scenario-based approach in handling the crisis which is escalating day by day contrary what IPCC (2008) study suggested for scenario-based approach to water resources management.

Nsubuga, et al (2014) analysis establishes drought periods which have led to the water level in Lake Victoria drop by a metre below the 10 year average and these droughts have significantly affected the communities’ water resources. Water levels in the lake are said to have been decreasing over time, with climate change (Mwiturubani, 2009).

In a wake to mitigate the climate change impacts on the water resources especially the Lake Victoria catchment basin, measures have been advanced in form of water governance. According to Nsubuga, et al (2014), water governance is seen as a range of political, social, economic and administrative systems that are in place to develop and manage water resources and the delivery of water services at different levels of society. However, currently climate change and the related increase in extreme weather events have exposed the vulnerability and lack of resilience of water resource management regimes. At the same time, policies to accommodate the prospects of climate and global change are absent. Consequently the conditions under which water resources managers have to perform have become increasingly unpredictable especially in a developing country like Kenya.

One of the factors influencing rainfall distribution in arid and semi-arid climates is the type of land use and land cover. Change in land use and land cover, particularly the decrease of forests has altered rainfall run-off and run-off infiltration processes. In East Africa, forested land is said to have decreased extensively in the last three decades or so, at the rate of between 1-4%, with a 2% reduction in forests in Kenya (Mwiturubani, 2009). The main reasons for deforestation include clearing forests and woodlands for agriculture and settlement, mining, wild fires, charcoal production and the overexploitation of wood resources for commercial purposes. All these activities contribute to the increase of carbon dioxide (CO2) in the atmosphere as the carbon sinks are progressively reduced, thus resulting to global warming.

The increasing pressure on water resources due to rapid population growth, increased urbanization and industrialization, uncontrolled environmental degradation and pollution have become a challenge on water resources management; making such areas prone to climate change and global warming manifestations like floods and droughts.  The frequent recurrence of extreme weather events (floods and droughts) and increasingly erratic rainfall are a big challenge to the management of Lake Victoria water resources. The variability in seasonal rainfall has significantly affected the different socio-economic activities that are heavily dependent on rainfall (Nsubuga et al, 2014).

The decrease or removal of vegetation as a result of prolonged droughts from the Earth’s surface tends to increase surface run-off and consequently reduces the infiltration capacity of the water. Furthermore, according to Mwiturubani (2009) the increase of surface run-off may increase soil erosion and hence the amount of eroded material that is transported and deposited in the rivers and streams. This, in turn, results in the decrease of the water storage capacity of the rivers and streams of the Lake Victoria water catchment area, and consequently natural water sources may become seasonal, flowing only during the rainy season, thus affecting the mechanisms of managing water resources.


Climate change and global warming have the potential to impact negatively on water availability, water quality, access to and demand for water in most countries around the globe, particularly in Africa. Climate change is likely to result in droughts and floods due to increases in temperatures which will exacerbate water scarcity with regard to access and use. It is argued that, owing to the decrease of the water supply for domestic use, livestock and crop production, hydropower production and industrial use, water-use, the socio-economic sector around the globe is at stake of a hurdle since the lives of the economy entirely depend on water as a resource. It is argued that the Lake Victoria Basin in particular, Kenya and East Africa in general, is experiencing dramatic rainfall changes and variations over time and space, resulting in a decrease of river flows and drying up of other many natural water sources; owing to climatic changes which continue to pose challenges on water resources management through its manifestations in form of unpredicted extreme weather conditions (droughts and floods).


This calls for the formulation and implementation of national policies and other legal frameworks that are geared towards addressing issues of climate change, particularly the adaptation to and mitigation of climate change impacts. It further calls for stakeholders’ dialogue to improve both customary and formal governance systems with regard to natural resources utilization and management. Since water resources touch every sector of the economy, it is important to improve water management in order to reduce the degradation of water sources and enhance equitable access to and utilization of the resource, thus reducing or alleviating sources of conflict pertaining to water access and utilization. It is therefore recommended that policymakers and planners integrate climate impact adaptation and mitigation measures in the formulation of policies and planning for development projects. It is further recommended that sector specific policies that relate to the hydrology of water resources, such as forestry, agriculture and mining, be reviewed to include issues of climatic change and variations and their effects. It is also necessary that countries that share trans-boundary natural resources such as water, share information on meteorological, hydrological and socioeconomic activities, and the way they are practiced in order to maximize the potential of the trans-boundary resources by minimizing tensions and conflicts that may otherwise result.

It is my contention therefore, that better information about this future will prepare us to do a better job in facing its challenges. Keeping in mind that the greatest risk in thinking about the future of climate-sensitive systems is to assume that the climate of the last century will be the climate we will face in the next as contended by Barnett et al. (2004).


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