Identifying Major Hydrologic Change Drivers in a Highly Managed Transboundary Endorheic Basin: Integrating Hydro-ecological Models and Time-Series Data Mining Techniques

American Geophysical Union (AGU) | August 23rd, 2022

The fragile balance of endorheic lakes in highly managed semi-arid basins with transboundary water issues has been altered by the intertwined effects of global warming an

The fragile balance of endorheic lakes in highly managed semi-arid basins with transboundary water issues has been altered by the intertwined effects of global warming and long-term water mismanagement to support agricultural and industrial demand. The alarming rate of global endorheic lakes’ depletion in recent decades necessitates formulating mitigation strategies for ecosystem restoration. However, detecting and quantifying the relative contribution of causal factors (climate variability and anthropogenic stressors) is challenging. This study developed a diagnostic multivariate framework to identify major hydrologic drivers of lake depletion in a highly managed endorheic basin with a complex water distribution system. The framework integrates the Soil and Water Assessment Tool (SWAT) simulations with time-series decomposition and clustering methods to identify the major drivers of change. This diagnostic framework was applied to the Salton Sea Transboundary Basin (SSTB), the host of the world's most impaired inland lake. The results showed signs of depletion across the SSTB since late 1998 with no significant changes in climate conditions. The time-series data mining of the SSTB water balance components indicated that decreases in lake tributary inflows (-16.4 Mm3 yr-2) in response to decline in Colorado River inflows, associated with state water transfer agreements, are causing the Salton Sea to shrink, not changes in the irrigation operation as commonly believed. The developed multivariate detection and attribution framework is useful for identifying major drivers of change in coupled natural-human systems.

Impacts of California’s Five-Year (2012-2016) Drought on Hydroelectricity Generation

Pacific Institute | April 13th, 2017

The severe hydrological drought afflicting California between 2012 and 2016 has ended, with an extremely wet winter beginning in October 2016. That five-year per

The severe hydrological drought afflicting California between 2012 and 2016 has ended, with an extremely wet winter beginning in October 2016. That five-year period was the driest and hottest in the instrumental record going back to the late 1800s. Impacts on communities, ecosystems, farmers, and the economy were widespread but have been unevenly distributed. The Pacific Institute has regularly analyzed the consequences of California droughts, beginning with comprehensive assessments of the 1987-1992 drought (Gleick and Nash 1991, Nash 1993), the 2007-2009 drought (Christian-Smith et al. 2011), and this most recent drought (Cooley et al. 2015, Gleick 2015, Cooley et al. 2016, Feinstein et al. 2017). This analysis is the third assessment of the impacts of the drought on hydropower production and greenhouse gas emissions from California’s energy sector (Gleick 2015, Gleick 2016). This analysis finds that during the five years ending September 30, 2016 (the end of the 2016 “water year”), hydropower generation was substantially below average, and the associated economic cost to California ratepayers was approximately $2.45 billion dollars. The additional combustion of fossil fuels for electricity generation also led to a 10 percent increase in carbon dioxide emissions from California’s in-state power plants (CARB 2015) along with increased emissions of other pollutants.

Impacts of California’s Ongoing Drought: Agriculture

Pacific Institute | August 26th, 2015

California’s agriculture sector has exceeded expectations during the most severe drought in recorded history at the cost of massive but unsustainable groundwater pumpin

California’s agriculture sector has exceeded expectations during the most severe drought in recorded history at the cost of massive but unsustainable groundwater pumping. Continued groundwater overdraft, while reducing the economic impacts of the drought for the agricultural sector now, has shifted the burden to others, including current and future generations forced to dig deeper wells, find alternative drinking water sources, and repair infrastructure damaged by subsidence. That is the conclusion of the new study, Impacts of California’s Ongoing Drought: Agriculture, released today by the Pacific Institute, an independent global water think tank. This new study is the first comprehensive analysis of the actual impacts of the drought on California agricultural revenue and employment through 2014 – the last year for which data are available. The study, drawing on data from the USDA National Agricultural Statistics Survey and the California Employment Development Department, analyzes acreage, revenue, and employment figures from 2000-2014. Production costs, impacts on animal or nursery products, or regional impacts are not examined because these data are not yet available. The study’s results provide critical insight into how the state can maintain a healthy agriculture sector in a future likely to see less water, more extreme weather, and greater uncertainty. California remains the largest agricultural producer in the U.S. in total output and in exports. During the drought, California’s agriculture sector has experienced record-high crop revenue and employment. Last year farmers harvested 640,000 fewer acres, which was 9 percent below pre-drought levels, yet crop revenue remained strong. Indeed, crop revenue peaked in 2013 at $34 billion – the highest level in California history. In 2014, crop revenue declined by $480 million, representing a 1.4 percent reduction from 2013 levels. All economic estimates have been corrected for inflation. Statewide agriculture-related jobs also reached a record-high of 417,000 people in 2014, highlighting the sector’s ability to withstand the reduction of available water.

Impacts of California’s Ongoing Drought: Hydroelectricity Generation

Pacific Institute | March 17th, 2015

California’s hottest and driest drought in recorded history is shifting the sources of energy for electricity with adverse economic and environmental consequences. The

California’s hottest and driest drought in recorded history is shifting the sources of energy for electricity with adverse economic and environmental consequences. The Pacific Institute, an internationally-renowned independent think tank focused on water issues, released a report that reveals diminished river flows have resulted in less hydroelectricity, more expensive electricity, and increased production of greenhouse gas emissions. “This severe drought has many negative consequences. One of them that receives little attention is how the drought has fundamentally changed the way our electricity is produced,” said the report’s author, Pacific Institute President Peter Gleick. “We hope this report prompts a lively debate on how to factor in a changing climate when we plan for electricity generation,” he added. Under normal conditions, electricity for the state’s millions of users is produced from a blend of many sources, with natural gas and hydropower being the top two. Since the drought has reduced the state’s river flows that power hundreds of hydropower stations, natural gas has become a more prominent player in the mix. This is an expensive change. According to the Institute’s report, between October 2011 and October 2014, California’s ratepayers spent $1.4 billion more for electricity than in average years because of the drought-induced shift from hydropower to natural gas. In an average year, hydropower provides 18 percent of the electricity needed for agriculture, industry, and our homes. Comparatively, in this three-year drought period, hydropower comprised less than 12 percent of total California electricity generation. A longer view reveals an even more startling economic impact: factoring in the dry years from 2007-2009, the total additional energy cost to the state’s electricity users during the six years of recent drought was $2.4 billion. This further reliance on natural gas for the state’s electricity production also has environmental costs. Hydropower produces few or no air contaminants, whereas burning natural gas emits many pollutants, including climate-changing greenhouse gases. During the 2011- 2014 drought period, burning more natural gas to compensate for limited hydropower led to an eight-percent increase in emissions of carbon dioxide and other pollutants from California power plants. If the current drought persists, water flowing to drive hydroelectric turbines will continue to shrink and expensive and polluting natural gas will become even more of a factor in the electricity production game.

Impacts of California’s Ongoing Drought: Hydroelectricity Generation 2015 Update

Pacific Institute | February 1st, 2016

The Pacific Institute has released a comprehensive assessment of the costs to California of lost hydroelectricity during the four years of drought from October 2011 to th

The Pacific Institute has released a comprehensive assessment of the costs to California of lost hydroelectricity during the four years of drought from October 2011 to the end of September 2015 (the official California “water year” runs from October 1 to September 30). Under normal conditions, electricity for the state’s millions of users is produced from a blend of many sources, with natural gas and hydropower being the top two. Since the drought has reduced the state’s river flows that power hundreds of hydropower stations, natural gas has become a more prominent player in the mix. This is an expensive change. According to the Institute’s new report, the four years of drought led to an increase in electricity costs of more than $2.0 billion. The additional combustion of fossil fuels for electric generation also led to a 10 percent increase in the release of carbon dioxide from California power plants. “The impacts of the California drought – which is the driest and the hottest in 120 years of instrumental records and one of the worst in history – has had widespread  impacts on all water users, including farmers, industries, cities, and natural ecosystems,” said the report’s author, Pacific Institute President Peter Gleick. “And in fact, all California ratepayers are affected by the drought as they pay for electricity that is both dirtier and more expensive than in non-drought years.” In addition, the report notes that the ability to expand California’s hydroelectric capacity is limited, as there are few undammed rivers, little unallocated water, and growing environmental, economic, and political constraints to adding new hydropower capacity.

Impacts of the California Drought from 2007 to 2009: Surprising Outcomes for California’s Agriculture, Energy, and Environment

Pacific Institute | June 16th, 2011

California’s three-year drought, which ended with this season’s cool and wet weather, had complicated and serious impacts that have been poorly understood and reporte

California’s three-year drought, which ended with this season’s cool and wet weather, had complicated and serious impacts that have been poorly understood and reported. Some of the impacts were expected; others were surprising. The Pacific Institute has just completed a nine-month assessment of new data from California’s agricultural, energy, and environmental sectors to evaluate actual consequences of the drought for the state. Analysis of state and federal data released over the past year finds that contrary to much of the media reporting, California’s agricultural community proved flexible and resilient, generating agri­cultural revenues in 2007, 2008, and 2009 that were the highest on record. And agriculture-related occupations remained a stable portion of total jobs available in areas directly impacted by water supply restrictions. Less frequently reported were the substantial impacts on energy production and aquatic ecosystems during the drought, which were economically and environmentally significant. “More severe drought is inevitable, and the U.S. – and California in particular – has not reformed drought monitoring, evaluation, planning, and response strategies the way other countries and regions have,” said Juliet Christian-Smith, senior research associate at the Pacific Institute and lead author of the report. “To become more resilient to future droughts, it will be critical to shift from crisis-driven responses to long-term mitigation strategies.” The Pacific Institute analysis, Impacts of the California Drought from 2007-2009, focused on three drought-sensitive sectors: agricultural production, energy production, and ecosystem health.  

Improving the Federal Response to Western Drought: Five Areas for Reform

Public Policy Institute of California (PPIC) | January 26th, 2016

The federal government is deeply involved in western water. It is the largest landowner, major supplier of irrigation, principal supporter of the farm sector, primary sou

The federal government is deeply involved in western water. It is the largest landowner, major supplier of irrigation, principal supporter of the farm sector, primary source of water information, and chief environmental regulator. For more than a century, western states have relied on a complex partnership with numerous federal agencies to manage water. The latest widespread drought has revealed both strengths and weaknesses in the federal role. To weather a warmer and possibly drier future, and to prepare for and respond to drought more effectively , the states and the federal government must address these weaknesses and work together to strengthen their partnership. Timely solutions are critical, given the growing vulnerability of the region’s residents, businesses, and environment to drought . This report identifies a suite of federal actions that can help weste rn states better manage drought . These reforms are, by design, modest and pragmatic. They focus on enhancing existing federal capacities, rather than implementing sweeping initiatives that would require time-consuming new funding or legislation.

Increased drought and extreme events over continental United States under high emissions scenario

Nature Portfolio (Springer Nature) | December 6th, 2023

Increased future occurrences of the exceptional 2018–2019 Central European drought under global warming

Nature Portfolio (Springer Nature) | August 6th, 2020

Since the spring 2018, a large part of Europe has been in the midst of a record-setting drought. Using long-term observations, we demonstrate that the occurrence of the

Since the spring 2018, a large part of Europe has been in the midst of a record-setting drought. Using long-term observations, we demonstrate that the occurrence of the 2018–2019 (consecutive) summer drought is unprecedented in the last 250 years, and its combined impact on the growing season vegetation activities is stronger compared to the 2003 European drought. Using a suite of climate model simulation outputs, we underpin the role of anthropogenic warming on exacerbating the future risk of such a consecutive drought event. Under the highest Representative Concentration Pathway, (RCP 8.5), we notice a seven-fold increase in the occurrence of the consecutive droughts, with additional 40 ( ±5 ) million ha of cultivated areas being affected by such droughts, during the second half of the twenty-first century. The occurrence is significantly reduced under low and medium scenarios (RCP 2.6 and RCP 4.5), suggesting that an effective mitigation strategy could aid in reducing the risk of future consecutive droughts.

Increased Interannual Precipitation Extremes over California under Climate Change

American Meteorological Society (AMS) | August 10th, 2015

Changes to mean and extreme wet season precipitation over California on interannual time scales are analyzed using twenty-first-century precipitation data from 34

Changes to mean and extreme wet season precipitation over California on interannual time scales are analyzed using twenty-first-century precipitation data from 34 global climate models. Models disagree on the sign of projected changes in mean precipitation, although in most models the change is very small compared to historical and simulated levels of interannual variability. For the 2020/21–2059/60 period, there is no projected increase in the frequency of extremely dry wet seasons in the ensemble mean. Wet extremes are found to increase to around 2 times the historical frequency, which is statistically significant at the 95% level. Stronger signals emerge in the 2060/61–2099/2100 period. Across all models, extremely dry wet seasons are roughly 1.5 to 2 times more common, and wet extremes generally triple in their historical frequency (statistically significant). Large increases in precipitation variability in most models account for the modest increases to dry extremes. Increases in the frequency of wet extremes can be ascribed to equal contributions from increased variability and increases to the mean. These increases in the frequency of interannual precipitation extremes will create severe water management problems in a region where coping with large interannual variability in precipitation is already a challenge. Evidence from models and observations is examined to understand the causes of the low precipitation associated with the 2013/14 drought in California. These lines of evidence all strongly indicate that the low 2013/14 wet season precipitation total can be very likely attributed to natural variability, in spite of the projected future changes in extremes.