Freshwater, drought, and climate change

Freshwater, drought, and climate change

Lack of freshwater for human consumption and agricultural use is a growing and very serious problem globally–including in rich countries like the United States.  As an example, rivers in many countries are experiencing significantly reduced flows due to warmer temperatures, longer and more frequent droughts, less snow and less winter precipitation, and the need to serve more and more people.

Quick bibliography: Recent research about the connection between freshwater supplies, drought, and the changing climate.

de Graaf, I.,E.M., Gleeson, T., Rens van Beek, ,L.P.H., Sutanudjaja, E. H., & Bierkens, M. F. P. (2019). Environmental flow limits to global groundwater pumping. Nature, 574(7776), 90-94. [Cited by]

“With a growing world population and continuing economic development, our freshwater resources are under simultaneous threat from increasing human water consumption and human-induced climate change, the latter of which will lead to more frequent and severe droughts. Already, groundwater is widely exploited, increasingly at rates that exceed recharge from rain and rivers over longer time periods and larger areas, leading to substantial and persistent drops in levels of groundwater and losses of groundwater from its storage.

Groundwater is the world’s largest freshwater resource and is critically important for irrigation, and hence for global food security. Already, unsustainable groundwater pumping exceeds recharge from precipitation and rivers, leading to substantial drops in the levels of groundwater and losses of groundwater from its storage, especially in intensively irrigated regions. When groundwater levels drop, discharges from groundwater to streams decline, reverse in direction or even stop completely, thereby decreasing streamflow, with potentially devastating effects on aquatic ecosystems. Here we link declines in the levels of groundwater that result from groundwater pumping to decreases in streamflow globally, and estimate where and when environmentally critical streamflows—which are required to maintain healthy ecosystems—will no longer be sustained. We estimate that, by 2050, environmental flow limits will be reached for approximately 42 to 79 per cent of the watersheds in which there is groundwater pumping worldwide, and that this will generally occur before substantial losses in groundwater storage are experienced. Only a small decline in groundwater level is needed to affect streamflow, making our estimates uncertain for streams near a transition to reversed groundwater discharge. However, for many areas, groundwater pumping rates are high and environmental flow limits are known to be severely exceeded. Compared to surface-water use, the effects of groundwater pumping are markedly delayed. Our results thus reveal the current and future environmental legacy of groundwater use.”

Elder, A. D., & Gerlak, A. K. (2019). Interrogating rainwater harvesting as do-it-yourself (DIY) urbanism. Geoforum, 104, 46-54.

For the first time in history, the global population is more concentrated in urban spaces than in rural areas. Population growth, climate change, and increasing stress on water resources evidence the urgency of adopting more sustainable urban water management practices. Drawing on contributions from the literature on informality, Do-It-Yourself (DIY) Urbanism, and urban rainwater harvesting, we investigate DIY Urbanism as a specific type of informality and as a strategy for citizen action to push local governments to adopt and institutionalize water sustainability initiatives. Taking the city of Tucson, Arizona, a pioneer of arid urban rainwater harvesting practices, as a case study, we examine rainwater harvesting as a proposed sustainable urban water management practice for a water-stressed city with aging infrastructure and a growing population particularly vulnerable to a changing climate. Based on interviews, stakeholder meetings, and document analysis, this paper examines several elements of the rainwater harvesting movement in Tucson that both mesh with and differ from other types of informality. We find that although rainwater harvesting contributes to the vision of an urban utopia for some local activists and NGO actors, for those working within the municipal bureaucracy, it may be viewed as an attack on social order and private resource rights. Despite some loss of autonomy in implementing DIY Urbanism after its institutionalization and emerging maintenance issues, DIY Urbanists in Tucson continue to challenge official authority to remake the city. We caution that the subsequent institutionalization of urban rainwater harvesting should not further institutionalize inequities in access but rather promote greater water democracy in cities.”

Li, Y., Guan, K., Peng, B., Franz, T. E., Wardlow, B., & Pan, M. (2020). Quantifying irrigation cooling benefits to maize yield in the US midwest. Global Change Biology, 26(5), 3065-3078.

“Irrigation is an important adaptation strategy to improve crop resilience to global climate change. Irrigation plays an essential role in sustaining crop production in water‐limited regions, as irrigation water not only benefits crops through fulfilling crops’ water demand but also creates an evaporative cooling that mitigates crop heat stress. Here we use satellite remote sensing and maize yield data in the state of Nebraska, USA, combined with statistical models, to quantify the contribution of cooling and water supply to the yield benefits due to irrigation. Results show that irrigation leads to a considerable cooling on daytime land surface temperature (−1.63°C in July), an increase in enhanced vegetation index (+0.10 in July), and 81% higher maize yields compared to rainfed maize. These irrigation effects vary along the spatial and temporal gradients of precipitation and temperature, with a greater effect in dry and hot conditions, and decline toward wet and cool conditions. We find that 16% of irrigation yield increase is due to irrigation cooling, while the rest (84%) is due to water supply and other factors. The irrigation cooling effect is also observed on air temperature (−0.38 to −0.53°C) from paired flux sites in Nebraska. This study highlights the non‐negligible contribution of irrigation cooling to the yield benefits of irrigation, and such an effect may become more important in the future with continued warming and more frequent droughts.”

Ruiz, D. M., Tallis, H., Tershy, B. R., & Croll, D. A. (2020). Turning off the tap: Common domestic water conservation actions insufficient to alleviate drought in the United States of America. PLoS One, 15(3), e0229798. [PDF]

“Climate change is exacerbating drought and water stress in several global regions, including some parts of the United States. Regionally, 30–40% of the western U.S. has experienced sustained drought in recent decades and the concurrence of drought and heat waves has increased in duration and frequency across the US from 1990–2010. Over the same time frame, human demand has increased in these areas leading to predictions that consumptive needs may not be met, such as along the Colorado River. During times of drought in the U.S., municipal governments, private water suppliers and non-profits commonly deploy advocacy campaigns and incentive programs targeting reductions in residential water use through actions including: repairing leaks, shutting off taps, and installing new water-saving appliances. We asked whether these campaigns have the potential to alleviate water stress during drought at the county scale by estimating the potential impact of full adoption of such actions. In 2010, we show that the maximum potential use reductions from these residential actions may only alleviate water stress in 6% (174) of U.S. counties. The potential impact of domestic programs is limited by the relative dominance of agriculture water withdrawal, the primary water user in 50% of U.S. counties. While residential actions do achieve some water demand savings, they are not sufficient to alter water stress in the majority of the continental U.S. We recommend redirecting advocacy efforts and incentives to individual behaviors that can influence agricultural water use.”

Jung‐Hee Ryu, Hayhoe, K., & Song‐Lak Kang. (2018). Projected changes in summertime circulation patterns imply increased drought risk for the South‐Central United States. Geophysical Research Letters, 45(20), 11,447-11,455. [Cited by]

“Water is already a scarce resource in the South‐Central United States. The region’s frequent droughts pit its agriculture community against the energy industry, ecosystem managers, and growing municipalities in competition for the region’s increasingly over‐allocated water resources. Our study identifies the daily weather patterns associated with historical drought and examines how these are likely to change as the world gets warmer. We find that the main weather pattern associated with drought, an isolated dome of high pressure centered over the South‐Central region, is likely to become stronger and more frequent by the late 21st century under human‐induced climate change. We also find that this appears to be related to self‐reinforcing ocean‐atmosphere interactions: in other words, the warmer the world gets, the stronger this pattern becomes. This is not good news for the region, as it establishes a physical mechanism that explains why projected summer rainfall is expected to decrease, and droughts to become stronger and longer, as climate continues to change.

For additional research about the connection between freshwater, drought, and climate change, please see the Science Primary Literature Database.

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