Drought and Rivers: Unraveling the Link and Long-Term Implications

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Droughts are silent disasters, steadily eroding river health and reshaping ecosystems. This article unravels how droughts affect rivers, inducing long-term consequences that ripple through our environment, economy, and communities. Are we prepared for a drier future?

Table of Contents

Dive in to learn more about this unseen crisis and why understanding its far-reaching implications is crucial for our survival and for the health of our planet.

The National Drought Mitigation Center provides a wealth of information about recognizing and managing drought conditions.

Droughts have affected more than 1 billion people globally in the last decadeEM-DAT
As of 2020, California’s ongoing drought has cost the state’s economy $2.7 billionUniversity of California, Merced.
An estimated 55 million people globally are directly affected by droughts every year, making it the most serious hazard to livestock and crops in nearly every part of the world.United Nations
Droughts can increase the risk of wildfires, with 70% of wildfires in the western US being caused by drought conditionsNational Interagency Fire Center
Droughts can lead to water scarcity, affecting over 1.9 billion people worldwideWorld Health Organization
In the US, droughts have caused an average annual economic loss of $9.5 billion over the past decadeNational Centers for Environmental Information
Droughts can impact agriculture, with an estimated 20% of global cropland experiencing drought conditionsFAO
The frequency and severity of droughts are increasing globally due to climate changeIPCC
Droughts can lead to water stress, with around 2.2 billion people lacking access to safely managed drinking water servicesUnited Nations
Droughts can have ecological impacts, leading to the loss of biodiversity and habitat degradationNature Conservancy

Key Takeaways

  1. Droughts have far-reaching impacts on rivers, ecosystems, communities, and industries.
  2. Reduced river flows during droughts can lead to habitat loss, disrupted life cycles, and fish deaths.
  3. Droughts also affect water quality, increase pollution concentrations, and contribute to algal blooms.

Recognizing the Drought

The impacts of drought on water quality river health and other factors are numerous and far-reaching, affecting not only wildlife and ecosystems but also human communities and industries. As climate change continues to exacerbate drought conditions worldwide, understanding these impacts becomes increasingly important for effective water management and community resilience.

Droughts are characterized by prolonged periods of low rainfall, leading to water shortages in affected areas. The severity of these droughts can vary, with some regions, such as the North Central Region of the United States, experiencing particularly intense and persistent drought conditions. This low rainfall has significant implications for all water users, from individual households to large industries, and can place additional stress on already struggling rivers.

Definition of a drought

A drought is defined geographically as a period of unusually persistent dry weather that persists long enough to cause significant problems such as crop damage, water supply shortage, or an imbalance in the ecosystem.

Droughts can occur in virtually any climate zone, from very wet to very dry. However, the characteristics and impacts of drought can significantly differ between climates. For example, what is considered a drought condition in a tropical rainforest may be considered normal in a desert.

Geographically, a drought is typically defined by its spatial distribution, severity, duration, and time of occurrence. Its spatial distribution refers to the size of the area affected, severity to the degree of moisture deficiency, duration to how long it lasts, and the time of occurrence to the time of year when it develops.

Several organizations like the United States Geological Survey (USGS) and the National Drought Mitigation Center provide various tools and maps to monitor and identify areas of drought geographically, often using indicators such as rainfall patterns, soil moisture, and vegetation health.

Drought in Numbers English Final 1 1 Drought and Rivers: Unraveling the Link and Long-Term Implications
Countries affected by drought in 2020 – 2022, source: UN

Impacts of Drought on Freshwater Wildlife and Ecosystems

Drought plays a significant role in changing the dynamics of freshwater environments. The most apparent impact is the dropping water levels in rivers, lakes, ponds, wetlands, and aquifers. For instance, the Colorado River Basin has seen a significant reduction in water volume due to prolonged drought, affecting the entire ecosystem.

Consequences of Reduced River Flows

The reduction in river flows leads to a decline in flushing rates, impacting the overall health of the river and its inhabitants. For example, Australia’s Murray-Darling Basin has experienced detrimental effects on its aquatic life due to decreased river flows during drought periods.

Loss of Habitat and Lifecycle Disruptions

Drought can lead to the loss of habitat for many species, eliminating essential features for aquatic life. The disruption of natural water flow and the drying of habitats can significantly affect animal life cycles. The California salmon population provides a stark example of this, where drought-induced low river levels have interrupted their breeding cycle.

Altered Flows and Reduced Stream Flow

Altered flows and reduced stream flow affect the physical and biological characteristics of water bodies. For instance, the Rio Grande River has been severely affected by these changes due to prolonged drought, impacting wildlife that relies on its waters.

Fish Death and Its Causes

Fish deaths during a drought can be attributed to high temperatures, low oxygen levels, and altered flows. An example is the mass fish deaths in the Darling River, Australia, which were attributed to these factors during a severe drought.

Impact on Native Fish Communities

The death of fish during a drought can have significant impacts on native fish communities. It can disrupt the balance of species in an ecosystem, and in severe cases, could lead to the local extinction of certain species. The USGS provides valuable information on this subject, emphasizing the interconnected nature of our freshwater ecosystems and the wide-reaching impacts of drought.

drought can impact freshwater ecosystems Drought and Rivers: Unraveling the Link and Long-Term Implications
Graphic showing how drought can impact freshwater ecosystems in the U.S. Caribbean, source: USGS

Impact of Drought on Water Quality and Pollution

Effects of Reduced River Flows on Pollutants

Drought conditions often lead to reduced river flows, which can in turn concentrate wastewater pollutants such as phosphates, nitrates, pharmaceuticals, and organic chemicals.

For instance, the Mississippi River experienced a severe drought in 2012 that led to the concentration of pollutants, affecting the aquatic life and overall health of the river. This concentration of pollutants can have detrimental effects on the health of a river and the organisms that live within it.

Stress on Freshwater Wildlife

The increased concentration of pollutants and nutrients during droughts can put significant stress on freshwater wildlife. They may struggle to adapt to the altered conditions and suffer from health issues due to the presence of these toxic substances.

An example is the 2014 drought in California, which led to increased concentrations of pollutants, causing stress and harm to local freshwater wildlife, particularly fish populations.

High Salinity

Another issue that arises during droughts is an increase in water salinity. As water bodies evaporate and reduce in size, the remaining water becomes saltier. High salinity levels can be harmful to many freshwater organisms, affecting their growth, reproduction, and survival.

During Australia’s Millennium drought from 1997 to 2009, many freshwater systems experienced increased salinity levels, impacting native aquatic species.

Blackwater Events

Drought conditions can also trigger blackwater events, where a large amount of organic material, such as leaves and bark, enters the waterways.

This occurred in the Murray-Darling Basin in Australia during the 2016 drought. The organic material depletes the oxygen in the water as it decomposes, causing widespread death of aquatic life. This phenomenon is yet another way droughts can impact water quality and the health of freshwater ecosystems.

High salinity and blackwater events are additional consequences of drought that can degrade water quality and harm aquatic life. The Environmental Protection Agency offers more information on these and other effects of drought on water quality.

Dissolved Oxygen Effects

Dissolved oxygen (DO) is an essential element for the survival of aquatic life forms, including fish and aquatic insects. It allows these organisms to respire underwater, much like how terrestrial creatures need oxygen in the air to survive.

Impact of Drought on Dissolved Oxygen Levels

Drought conditions can drastically affect the levels of dissolved oxygen in freshwater bodies. This happens due to reduced river flow speeds, stagnation, and increased water temperatures that are often associated with droughts. As water flow decreases, less oxygen is mixed into the water, leading to reduced DO levels.

Consequences of Low-Dissolved Oxygen

The consequences of low dissolved oxygen can be dire for aquatic ecosystems. Under such conditions, fish and other oxygen-dependent organisms can struggle to survive, often resulting in what is known as “fish kills”. In severe cases, these conditions can even lead to the local extinction of certain aquatic species. It is a stark reminder of the far-reaching impacts that drought can have on our water systems and the life they support.

dissolved oxygen?
What is dissolved oxygen?, source: apureinstrument.com

Algal Growth Problems

The Interplay between River Flow and Algal Blooms

The balance of algal growth in water bodies is delicate and greatly influenced by river flow. During droughts, reduced river flow can disrupt this balance, often leading to an overgrowth of algae. For instance, the Mississippi River experienced an explosive growth of algae during the 2012 drought.

The Domino Effect of Algal Blooms

When river flow decreases, algal reproduction can increase, leading to the formation of harmful algal blooms. These blooms can be detrimental to the river ecology, affecting aquatic plants and altering dissolved oxygen concentrations. One notable example is the algal bloom in Lake Erie, which resulted in significant oxygen depletion.

The Threat of Cyanobacterial Blooms

The increased algal blooms during drought can also lead to the prevalence of cyanobacterial blooms. These are harmful blooms that can release toxins and are particularly common during summer drought periods, as seen in Florida’s Lake Okeechobee.

algal blooms
Algal blooms

The Prolonged Impact of Drought on Riverine Ecosystems

Altering Fish Communities and Interactions

Over time, droughts can drastically reshape fish communities. These climatic events can disturb the delicate balance of species interactions, possibly leading to an unstable ecosystem.

Restricting Species Life Events

Drought conditions may also hinder important life events in aquatic species, like upstream migration, a critical process for many fish species during breeding seasons.

Endemic Species Loss and Species Shifts

Persistent drought can be especially detrimental to endemic species, possibly leading to their local extinction. This, in turn, can cause shifts in the balance between native and non-native species in our rivers. For instance, the prolonged drought in the Colorado River Basin has been linked to the decline in native fish species.

Endemic fish Species Loss

Actions to Mitigate Drought Impact on Rivers

Restricting Livestock Access

One of the immediate actions that can be taken is restricting livestock access to water bodies, particularly during severe drought conditions. This can prevent overgrazing along river banks and reduce contamination from animal waste.

Adopting Conscious Fishing Practices

Conscious fishing practices, such as catch and release or respecting fishing seasons, can help conserve fish populations during periods of drought.

Water-Saving Measures in Agriculture and Industry

In agriculture and other industries that use significant amounts of water, implementing water-saving measures can help reduce the pressure on our rivers. This can include techniques like drip irrigation in agriculture or water recycling in manufacturing.

Enhancing Water Storage Infrastructure

Upgrading water storage infrastructure, such as dams and reservoirs, can also be a proactive measure. This helps store excess water in times of plenty, ensuring a more consistent supply during drought periods.

Promoting Water Conservation in Communities

Community engagement in water conservation is another critical step. Encouraging households to reduce water usage can alleviate the demand pressure on freshwater sources.

Restoring and Protecting Wetlands

Wetlands act as natural sponges, absorbing excess water during river floods and releasing it during dry periods. Restoring and protecting these ecosystems can help maintain water levels in rivers during droughts.

Implementing Sustainable Land Management Practices

Sustainable land management practices, such as maintaining vegetative cover to reduce runoff and enhance soil moisture retention, can also contribute to mitigating the impacts of drought on rivers.

These actions, while not exhaustive, provide a starting point for managing the effects of drought on rivers and the diverse life they support.

Organizations like the World Wildlife Fund offer resources on these and other strategies for mitigating the effects of drought.

drought Drought and Rivers: Unraveling the Link and Long-Term Implications

Impact of Drought on Communities

Socio-Economic Consequences of Drought

Drought can significantly affect human communities, especially those reliant on agriculture or fishing. Decreased water availability can lead to crop failure, livestock death, and decreased fish populations. These outcomes can result in job loss, reduced income in these sectors, and increased food prices, which puts financial strain on community members.

Industries dependent on water, like tourism, recreation, and manufacturing, can also suffer economic downturns. Resources like the United States Drought Monitor can provide crucial information to communities facing these challenges.

Health Impacts of Drought

Drought can also lead to direct and indirect health impacts. Issues like dehydration, heatstroke, and dust-related respiratory problems can become more common. Moreover, mental health implications, such as stress and anxiety related to economic instability and uncertainty, are important to consider. There is also an increased risk of waterborne diseases due to decreased water quality and sanitation challenges during droughts.

Social Issues Arising from Drought

Potential social issues may also arise, such as increased migration and conflict over scarce water resources. For a deeper understanding of these social and health impacts, the World Health Organization provides extensive resources. Understanding these impacts is key to developing effective community resilience strategies in the face of drought.

Impact on Infrastructure and Services

Drought can severely impact community infrastructure and services. For example, strain on water supply systems due to decreased availability and increased demand can disrupt daily life and business operations. Reduced water levels can affect the functionality of hydroelectric power plants, leading to energy shortages.

The risk of wildfires also increases during drought periods, leading to further infrastructure damage and putting strain on emergency services.

Adaptive Measures and Community Resilience in the Face of Drought

Despite these challenges, communities can adopt adaptive measures to build resilience in the face of drought. Drought preparedness and planning are key to mitigating impacts on communities. Measures such as water-efficient practices, diversification of income sources, and mental health support initiatives can help communities withstand and recover from the effects of drought.

The role of government and community leaders is crucial in implementing effective drought response strategies, improving infrastructure, and promoting sustainable water management. Resources like the American Water Works Association provide valuable information for communities seeking to enhance their resilience to drought.

Understanding the impacts of drought on our waterways and communities is the first step toward a more resilient future. As we continue to face the challenges of climate change, it’s more important than ever to take action to mitigate the effects of drought and protect our most precious resource – water.


Can rivers and lakes recover from drought?

Yes, rivers and lakes can recover from drought once sufficient rainfall replenishes the water sources. However, the recovery process may vary depending on the severity and duration of the drought and the resilience of the ecosystem.

What is the main effect of hydrological drought?

The main effect of hydrological drought is a significant decrease in water availability in rivers, lakes, and groundwater sources. This can lead to reduced water levels, drying up of water bodies, and limited access to water for various uses, impacting ecosystems, agriculture, and communities.

What river in the US is drying up?

Several rivers in the US have experienced drying up or reduced water flows during droughts. Examples include the Colorado River, which has faced persistent drought conditions and reduced water levels, and the Rio Grande, which has also been significantly impacted by drought and water scarcity in recent years.

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Author: Richard
Meet Richard Buettner, the esteemed editor of GeoAffairs, armed with a Master's degree in Geography and sharing his valuable insights through 25 years of dedicated experience in the field.

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