Brian D. Richter

The Nature Conservancy · Global Freshwater Program

Around the world, water rights systems govern the allocation of water to a multitude of users. Such systems primarily come into play during times of drought, when some users have to be shorted. Yet their management during times of excess can have implications for subsequent drought impacts. This is evident in the State of Colorado, where under “fre...

Persistent overuse of water supplies from the Colorado River during recent decades has substantially depleted large storage reservoirs and triggered mandatory cutbacks in water use. The river holds critical importance to more than 40 million people and more than two million hectares of cropland. Therefore, a full accounting of where the river’s wat...

The Rio Grande-Rio Bravo's flow regime has been highly altered for more than 130 years, yet the river ecosystem still supports important biodiversity including numerous endangered species. More than 80% of water consumed in the basin goes to irrigating farms, but in recent decades, farmers have repeatedly experienced severe water shortages. Given t...

Irrigated agriculture dominates freshwater consumption globally, but crop production and farm revenues suffer when water supplies are insufficient to meet irrigation needs. In the United States, the mismatch between irrigation demand and freshwater availability has been exacerbated in recent decades due to recurrent droughts, climate change and ove...

Sustainable agricultural water systems are critical to ensure prosperous agricultural production, secure water resources, and healthy ecosystems that sustain livelihoods and well-being. Many growing regions are using water unsustainably, leading to groundwater and streamflow depletion and polluted water bodies. Often, this is driven by global consu...

Environmental flows (e-flows) aim to mitigate the threat of altered hydrological regimes in river systems and connected waterbodies and are an important component of integrated strategies to address multiple threats to freshwater biodiversity. Expanding and accelerating implementation of e-flows can support river conservation and help to restore th...

Nearly one-sixth of U.S. river basins are unable to consistently meet societal water demands while also providing sufficient water for the environment. Water scarcity is expected to intensify and spread as populations increase, new water demands emerge, and climate changes. Improving water productivity by meeting realistic benchmarks for all water...

Human consumption of freshwater is now approaching or surpassing the rate at which water sources are being naturally replenished in many regions, creating water shortage risks for people and ecosystems. Here we assess the impact of human water uses and their connection to water scarcity and ecological damage across the United States, identify prima...

In the decade since the Brisbane Declaration (2007) called upon governments and other decision makers to integrate environmental flows into water management, practitioners have continued to seek ways to expand implementation of flow restoration or protection. The science and practice of environmental flow assessment have evolved accordingly, genera...

We present an improved water-scarcity metric we call water depletion, calculated as the fraction of renewable water consumptively used for human activities. We employ new data from the WaterGAP3 integrated global water resources model to illustrate water depletion for 15,091 watersheds worldwide, constituting 90% of total land area. Our analysis il...

Brian Richter, a global leader in water science and conservation, in his book, ?Chasing Water' formulates seven principles that are beneficial for a sustainable water future. The first one is building a shared vision for your community's water structure. Community engagement is proving to be instrumental in gaining acceptance for proposals to incre...

An age-old conflict around a seemingly simple question has resurfaced: why do we conserve nature? Contention around this issue has come and gone many times, but in the past several years we believe that it has reappeared as an increasingly acrimonious debate between, in essence, those who argue that nature should be protected for its own sake (intr...

Existing water governance systems are proving to be quite ineffective in managing water scarcity, creating severe risk for many aspects of our societies and economies. Water markets are a relatively new and increasingly popular tool in the fight against growing water scarcity. They make a voluntary exchange possible between interested buyers and se...

Capping water use in a place that is challenged with water scarcity will likely seem counterintuitive to many governments or water planners. The Murray-Darling Basin Ministerial Council's rationale and the historical events that led to the Cap offer some important lessons for other states and countries struggling with water scarcity, from Californi...

City water planners are finding it increasingly difficult to secure additional water supplies in many water-short regions. The ability to acquire new water supplies by purchasing permanent water rights or leasing water on temporary basis is providing new options for city water planners in some parts of the world, including the western US. By purcha...

As the year 2012 drew to a close, the U.S. Bureau of Reclamation published the results of a comprehensive study of the Colorado River watershed in the western United States. The final report of the Colorado River Basin Water Supply and Demand Study summarized more than 150 different ideas for balancing the water budget of the Colorado River. One of...

I am regularly asked how I can remain optimistic in spite of what I know about the world’s water challenges. There certainly is plenty of depressing news about water shortages being reported in the global news media. The Internet search engine that I have set up on my computer automatically delivers a continual stream of stories about water struggl...

A few years ago, I was asked to join a panel of speakers at a national conference on water scarcity. One of my fellow panelists was a farmer from Florida. After he listened to many presentations by others, the farmer was obviously anxious to get in a word. He confidently proclaimed that there is no such thing as water scarcity. He asserted that con...

“People used to think that it was a curse from God. Some people thought that they were bewitched. But later we came to realize that it was those dams. The dams are swallowing a lot of water. Now water cannot come here.”

Abu Khalil, a cotton grower forced to abandon his Syrian farm because of a lack of water in 2013, was interviewed by columnist Thomas Friedman for the New York Times.1 Friedman described severe water shortages in Syria as a primary culprit in sparking the tumultuous civil revolt that swept across the country beginning in 2011. “We could accept the...

Globally, corporations and industry are seeking to secure access to sufficient quantities of water to meet current and future needs in a socially, economically and environmentally responsible way in the midst of an unfolding global water crisis with risks that transcend communities, industry and the environment. Through a business case centered on...

Brian Richter, director of Global Freshwater Strategies at The Nature Conservancy, analyzed urban water supply challenges from global and local perspectives in a study. Using a global water model, he examined how water is being used in the local watersheds of water-stressed cities around the world. He found that more than 90% of all consumptive wat...

Cities around the world are struggling to access additional water supplies to support their continued growth because their freshwater sources are becoming exhausted. Half of all cities with populations greater than 100,000 are located in water-scarce basins, and in these basins agricultural water consumption accounts for more than 90% of all freshw...

The vast majority of the world's rivers are now being tapped for their water supplies, yet only a tiny fraction of these rivers are protected by any sort of environmental flow standard. While important advances have been made in reducing the cost and time required to determine the environmental flow needs of both individual rivers and types of rive...

Freshwater scarcity is a growing concern, placing considerable importance on the accuracy of indicators used to characterize and map water scarcity worldwide. We improve upon past efforts by using estimates of blue water footprints (consumptive use of ground- and surface water flows) rather than water withdrawals, accounting for the flows needed to...

Global maps of monthly natural runoff in the world's major river basins. (TIF)

Global maps of the monthly blue water footprint in the world's major river basins. Period 1996–2005. (TIF)

Monthly blue water scarcity for the world's major river basins. (PDF)

Global river basin map. (TIFF)

Monthly blue water footprint for the world's major river basins. (PDF)

Monthly blue water availability for the world's major river basins. (PDF)

Global maps of monthly blue water availability in the world's major river basins. (TIF)

Monthly natural runoff for the world's major river basins. (PDF)

Bioenergy expansion can significantly impact water resources in the region in which it occurs. Investment, policy, and resource management decisions related to bioenergy should therefore take this critical consideration into account. Water resource impacts can defy easy quantification because water consumption varies spatially and temporally, diffe...

A nationwide poll conducted by The Nature Conservancy and Fairbank, Maslin, Maullin, Metz & Associates, asked questions regarding the source of water used by the residents. 77% were unable to correctly identify their source of drinking water. Of the respondents who said that they could indeed identify their water source, only about half did so corr...

Climate change is predicted to affect the future supply and demand for water resources. Current water management practices may not adequately cope with the impacts of climate change on the reliability of water supply, flood risk, health, agriculture, energy generation and aquatic ecosystems. Water managers can adapt to climate variability by struct...

Climate change is expected to have significant impacts on hydrologic regimes and freshwater ecosystems, and yet few basins have adequate numerical models to guide the development of freshwater climate adaptation strategies. Such strategies can build on existing freshwater conservation activities, and incorporate predicted climate change impacts. We...

The World Commission on Dams (WCD) report documented a number of social and environmental problems observed in dam development projects. The WCD gave particular emphasis to the challenges of properly resettling populations physically displaced by dams, and estimated the total number of people directly displaced at 40-80 million. Less attention has...

1. The flow regime is a primary determinant of the structure and function of aquatic and riparian ecosystems for streams and rivers. Hydrologic alteration has impaired riverine ecosystems on a global scale, and the pace and intensity of human development greatly exceeds the ability of scientists to assess the effects on a river‐by‐river basis. Curr...

Flooding is the most damaging natural disaster worldwide, and the flood-vulnerable population is expected to grow in coming decades (1). Flood risks will likely increase because of both climate change (1) and shifting land uses, such as filling of wetlands and expansion of impervious surfaces, that lead to more rapid precipitation runoff into river...

Attempts to implement environmental flows have encountered many obstacles. Many water allocation systems include a system of prioritization among water uses that generally does not favor environmental flow protection, or do not allow for protection of high flow events for ecological purposes. It has proven very difficult to implement complicated en...

Rivers provide a special suite of goods and services valued highly by the public that are inextricably linked to their flow dynamics and the interaction of flow with the landscape. Yet most rivers are within watersheds that are stressed to some extent by human activities including development, dams, or extractive uses. Climate change will add to an...

The development of water resources to satisfy urban water needs has had serious impacts on freshwater ecosystem integrity and on valuable ecosystem services, but positive trends are emerging that point the way toward a solution. We demonstrate this through case studies of water resource development in and around five large urban areas: Los Angeles,...

This article discusses the idea of water stewardship certification in light of the fact that with the human population approaching 7 billion, the world is facing the limits of earth's freshwater resources. The article presents other issues that contribute to the problem of sustainability of the earth's water supply, and urges the implementation of...

  River scientists are increasingly asked to provide recommendations about the amount and timing of water flows needed to support ecosystem health. The need for scientifically credible environmental flow assessments and the limited availability of resources to conduct in-depth studies place a premium on methods that can be readily applied at low co...

A lot of hydro power companies are now planning and constructing a hydro power dams as an alternative source of energy. Among companies that planned and constructed hydro power dams are the China Three gorges Power Corporation (CTGPC) of which declared another four set of dams project of the which the two of four dams will be located on the upper m...

Rivanna Water and Sewer Authority (RWSA), which operates three reservoirs in the Rivanna River Basin to supply water to the outlying areas in Albemarle County has implemented stringent and mandatory water conservation measures to be able to survive the drought. Throughout the planning process, local environmental interests argued strongly for bette...

"The construction of new dams has become one of the most controversial issues in global efforts to alleviate poverty, improve human health, and strengthen regional economies. Unfortunately, this controversy has overshadowed the tremendous opportunity that exists for modifying the operations of existing dams to recover many of the environmental and...

The Nature Conservancy (TNC) is collaborating with AWWA and other organizations to assist water managers in protecting public health and safety while also protecting freshwater ecosystems and meeting the water supply needs of the community. A consortium led by TNC and AWWA has been started to evaluate effort that would recognize water utilities tha...

Many river restoration projects are focusing on restoring environmental flow regimes to improve ecosystem health in rivers that have been developed for water supply, hydropower generation, flood control, navigation, and other purposes. In efforts to pre-vent future ecological damage, water supply planners in some parts of the world are beginning to...

We agree with Kanivetsky and Shmagin ( Eos, 86 (50) 2005) that better accounting of flows comprising the hydrologic cycle is needed and that better quantification of recharge (into groundwater) and discharge (i.e.,streamflow) is important from human and environmental perspectives. However, because these authors promote their approach as being usefu...

The development of water resources to satisfy urban water needs has had serious impacts on freshwater ecosystem integrity and on valuable ecosystem services, but positive trends are emerging that point the way toward a solution. We demonstrate this through case studies of water resource development in and around five large urban areas: Los Angeles,...

Real and apparent conflicts between ecosystem and human needs for fresh water are contributing to the emergence of an alternative model for conducting river science around the world. The core of this new paradigm emphasizes the need to forge new partnerships between scientists and other stakeholders where shared ecological goals and river visions a...

Human demands on the world's available freshwater supplies continue to grow as the global population increases. In the endeavor to manage water to meet human needs, the needs of freshwater species and ecosystems have largely been neglected, and the ecological consequences have been tragic. Healthy freshwater ecosystems provide a wealth of goods and...

Water managers, scientists and conservationists around the world are now exploring ways to meet human needs for water while keeping river ecosystems healthy. This requires identifying the amount and timing of water flows that must remain in rivers to sustain their ecological health. This is a challenging scientific endeavor, because river flow infl...

Human society has used freshwater from rivers, lakes, groundwater, and wetlands for many different urban, agricultural, and industrial activities, but in doing so has overlooked its value in supporting ecosystems. Freshwater is vital to human life and societal well-being, and thus its utilization for consumption, irrigation, and transport has long...

Human society has used freshwater from rivers, lakes, groundwater and wetlands for many different urban, agricultural, and industrial activities, but in doing so has overlooked its value in supporting ecosystems. Freshwater is vital to human life and societal well-being, and thus its utilisation for consumption, irrigation, and transport has long t...

Biodiversity conservation has become the stated objective of national governments, state agencies, local communities, and scientific organizations. Yet despite this attention the term biodiversity remains poorly defined. One of the unfortunate consequences of this lack of definition is a proliferation of claims that biodiversity can be both used an...

The composition and structure of native riverine ecosystems are tightly linked to natural hydrologic variability. By managing river flows for water supplies and power generation, water management agencies have inadvertently caused considerable degradation of riverine ecosystems and associated biodiversity. New approaches for meeting human needs for...

Approaches to conservation and natural resource management are maturing rapidly in response to changing perceptions of biodiversity and ecological systems. In past decades, biodiversity was viewed largely in terms of species richness, and the ecosystems supporting them were seen as static adn predictable(Fielder et.al. 1997). Conservation activitie...

Like most conservation scientists, our career choices were motivated by a strong desire to save the world. Reflecting back on our academic training, we realize that we were taught a great deal about the natural world but not much about how to save it. The natural and physical sciences curricula we were exposed to in academia provided little guidanc...

Maintaining natural hydrologic variability is essential in conserving native riverine biota and river ecosystem integrity. Hydrologic variation plays a major role in structuring the biotic diversity within river ecosystems as it controls key habitat conditions within the river channel, the floodplain, and hyporheic (stream-influenced ground water)...

Maintaining natural hydrologic variability is essential in conserving native riverine biota and river ecosystem integrity. Hydrologic variation plays a major role in structuring the biotic diversity within river ecosystems as it controls key habitat conditions within the river channel, the floodplain, and hyporheic (stream-influenced ground water)...

umans have long been fasci- nated by the dynamism of free-flowing waters. Yet we have expended great effort to tame i rivers for transportation, water sup- ply, flood control, agriculture, and ; f

Threats to imperiled freshwater fauna in the U.S. were assessed through an experts survey addressing anthropogenic stressors and their sources. Specifically, causes of historic declines and current limits to recovery were identified for 135 imperiled freshwater species of fishes, crayfishes, dragonflies and damselflies, mussels, and amphibians. The...

Threats to imperiled freshwater fauna in the U.S. were assessed through an experts survey addressing anthropogenic stressors and their sources. Specifically, causes of historic declines and current limits to recovery were identified for 135 imperiled freshwater species of fishes, crayfishes, dragonflies and damselflies, mussels, and amphibians. The...

1. This paper introduces a new approach for setting streamflow‐based river ecosystem management targets and this method is called the ‘Range of Variability Approach’ (RVA). The proposed approach derives from aquatic ecology theory concerning the critical role of hydrological variability, and associated characteristics of timing, frequency, duration...

Hydrologic regimes play a major role in determining the biotic composition, structure, and function of aquatic, wetland, and riparian ecosystems. However, human land and water uses are substantially altering hydrologic regimes around the world. Improved quantitative evaluations of human-inducedhydrologic changes,are needed,to advance research on th...

Groundwater depletion threatens many riparian ecosystems in arid and semiarid regions of the world. The aquifer that sustains Arizona's San Pedro River riparian ecosystem, for example, is threatened by regional groundwater declines and localized pumping from the alluvial aquifer. This paper demonstrates the important role of shallow groundwater in...

During more than 40 years of conservation activity, The Nature Conservancy has played an instrumental role in the protection of biodiversity by assessing the rarity of species and communities, tracking their locations and ecological status, and pursuing some form of conservation management for critical habitats. The acquisition of key private lands...

In March 1991 a 10-year return flood (368 m³s⁻¹) occurred in the Hassayampa River, a perennial stream (0.1 m³s⁻¹ base flow) within the Sonoran Desert. Depth of the floodwater ranged from 2.64 ± 0.20 m (mean ± SD) near the stream to 0.47 ± 0.31 m in the highest floodplain zone (Prosapis forest). Flow velocity was 1.7 ± 0.6 m s⁻¹ and 0.9 ± 0.4 m s⁻¹...

In the Hassayampa River system, recruitment of Fremont cottonwood Populus fremontii and Goodding willow Salix gooddingii, depends on 1) large prior-year floods to remove herbaceous cover; 2) high spring flows or rains to stimulate germination on floodplains above the zone of frequent flood inundation; and 3) reduced post-germination flooding to red...

Urban construction activities can increase sediment loading rates as much as 40,000 times the rate that occurs from an undeveloped farm or woodland in an equivalent period of time. The Castle Pines and Castle Pines North Metropolitan districts have developed a comprehensive erosion control program for their communities, which is expected to effecti...