Designing Drought Indicators

American Meteorological Society (AMS) | November 25th, 2019

Drought indicators hold great potential to assist water management. However, drought information products are traditionally designed by scientists with little input from

Drought indicators hold great potential to assist water management. However, drought information products are traditionally designed by scientists with little input from the end users. This has resulted in an inundation of products ill suited to stakeholder needs and requirements, limiting the potential for improving management through the use of these products. In a different field—the field of product design—product designers and strategists have matured methodologies for optimizing the creation of material products, such as shoes and cars, for example, for customers. A multitude of design-centric strategies are employed to determine customer needs and requirements (e.g., lighter shoe, more cushioning, breathable, reflectivity, arch support, width options, color options). These approaches can be extended from material to information or data products. Here, we describe how the methodological approaches within the field of product design can be interdisciplinarily employed to data products for drought indicators, with water managers as end users (i.e., the “customers”). New results for drought data products may be transformative in how drought indices are constructed, communicated, and delivered, with potentially significant improvements for water management.

Development and Interpretation of Daily Seasonal Water Supply Forecasts

U.S. Department of Agriculture (USDA) | February 26th, 2009

This Technical Note documents the process used to develop the Daily Water Supply Forecast procedures and serves as a guide for helping users interpret the results. Thi

This Technical Note documents the process used to develop the Daily Water Supply Forecast procedures and serves as a guide for helping users interpret the results. This product was developed to supplement official water supply forecasts generated at the beginning of each month during the water supply season. The water resource community requested daily calibrated water supply forecasts to aid in the assessment of increased climate variability. The Natural Resources Conservation Service (NRCS) National Water and Climate Center (NWCC) developed these procedures that use hydroclimatic data collected by the SNOTEL and USGS data networks.

Disparities in urban vegetation degradation and heat exposure during drought periods in U.S. cities

nature Portfolio (Springer Nature) | December 15th, 2025

Policymakers are increasingly recognizing the necessity for the equitable distribution of urban green spaces across sociodemographic groups. Nevertheless, the extant rese

Policymakers are increasingly recognizing the necessity for the equitable distribution of urban green spaces across sociodemographic groups. Nevertheless, the extant research consistently highlights disparities in this allocation, frequently neglecting the critical implications of extreme droughts on vegetation-related inequalities. Leveraging satellite observations in conjunction with census data, we examine the drought-related disparities in urban vegetation degradation (UVD) and the corresponding heat exposure across sociodemographic groups within major U.S. cities. Our findings reveal that marginalized communities experience more severe UVD during droughts, a trend particularly pronounced in Sunbelt U.S. cities, such as those in Southern California and Texas. Additionally, the unequal UVD during drought exacerbates existing inequalities in heat exposure. These results highlight the urgent need for the implementation of targeted policies, including effective water supply management strategies. Such measures could mitigate thermal environmental injustices and promote equitable vegetation distribution under a warming climate.

Drought and ozone air quality in California: Identifying susceptible regions in the preparedness of future drought

Environmental Research (Elsevier) | October 19th, 2022

California experienced extreme and prolonged drought conditions during the early 2010s. To date, little is known regarding the influence of drought on air quality. Our st

California experienced extreme and prolonged drought conditions during the early 2010s. To date, little is known regarding the influence of drought on air quality. Our study quantified site-specific associations between drought (defined by the Standardized Precipitation-Evapotranspiration Index; SPEI) and daily maximum 8-h ozone (O3) concentrations for California, USA, and then pooled these associations for the years 2009–2015. Overall, ambient O3 concentration was higher during droughts by 1.18 ppb (95% confidence interval (CI) = 1.00–1.36). The sensitivity of O3 to drought was greater during the warm season than during the cool season (1.73 ppb versus 0.79 ppb higher O3 during droughts) with substantial regional variation. In a pooled analysis with meteorological parameters as potential effect modifiers, the spatial heterogeneity of drought-O3 associations was explained strongly by average relative humidity for each season (71.9% (warm season) and 73.4% (cool season) of the drought-O3 associations explained), followed by the drought-related changes in relative humidity (47.6% (warm season)) and temperature (53.6% (cool season)). The pooled regression further identified regions susceptible for drought-related O3 increases as those with relatively low average relative humidity (10–25th percentiles or 44.3–47.3%) and larger drought-related decrease in relative humidity and increase in temperature. As the drought events are projected to occur with increased frequency and intensity in the era of climate change, the excess health burdens from O3 exposures attributed to the projected drought events need to be taken into account when allocating air quality and health resources. The impacts of O3 on health during droughts would confound the health burdens from the drought itself.

Drought and the California Delta—A Matter of Extremes

University of California, Davis (UC Davis) | July 14th, 2014

California is in an extreme drought as a result of low precipitation in water year 2012, record low precipitation in 2013, and the remarkably dry first few months of 2014

California is in an extreme drought as a result of low precipitation in water year 2012, record low precipitation in 2013, and the remarkably dry first few months of 2014. We typically receive our largest precipitation totals in Decembers and Januaries (which provide about 36% of the precipitation in the Delta’s catchment), and when those months are as dry as they were this year, subsequent months have to be unseasonably wet to avoid drought. Most of the current winter, especially December 2013–January 2014, was dry because a persistent ridge of high (atmospheric) pressures set up offshore, diverting storms away from California and into Alaska. That same diversion gave the Delta’s catchment its warmest winter in 120 years, as well as bringing all that cold weather to the eastern US. While the February 2014 storms provided minor relief and momentarily slowed the spiral into deeper drought, the drought continues apace. Nonetheless, as harsh as it is, the current drought is not unprecedented in the Delta’s history, and even less so in its prehistory. In this essay, we consider the ways that droughts in California arise from a few missing storms and from long-term variations and changes in climate, in order to identify drought-science needs for Delta management. 

Drought and Water Year 2016: Hot and Dry Conditions Continue

California Department of Water Resources (DWR) | September 15th, 2016

Drought is a recurring feature of California’s climate. Paleoclimate information, such as streamflow or precipitation reconstructions developed from tree-ring d

Drought is a recurring feature of California’s climate. Paleoclimate information, such as streamflow or precipitation reconstructions developed from tree-ring data, can provide a perspective on long-term climate variability. Reconstructed hydrologic records show that California has experienced droughts of much longer duration than those in our century- plus recorded historical period. There is, however, one drought within the historical period on a par with driest events in the paleo record, if the comparison is made using driest 10-year streamflow periods. The prolonged off-and-on dry conditions of the 1920s-30s were severe in terms of their hydrology, but they occurred at a time when the state’s population was in the ballpark of 6 million and irrigated acreage was less than half of present levels.

Drought Attribution Studies and Water Resources Management

American Meteorological Society (AMS) | February 16th, 2023

Drought impact on cropland use monitored with AVIRIS imagery in Central Valley, California

Science of the Total Environment (Elsevier) | November 19th, 2022

During 2012–2016 California experienced the longest and most severe drought in the last centuries. This water scarcity led to an increase in non-cultivated croplands du

During 2012–2016 California experienced the longest and most severe drought in the last centuries. This water scarcity led to an increase in non-cultivated croplands during this period. The objective of this study was to quantify agricultural trends in the Central Valley (California) at peak growth from 2013 to 2016 during the drought and in 2017–2018 post-drought. For this purpose, we analysed yearly official harvested area reported at county level for the main crops and compared them to visible-shortwave infrared (VSWIR) spectra acquired by the Airborne Visible/Infrared Imaging-Spectrometer (AVIRIS-classic) over 2334 km2 of the Central Valley each year. Multiple Endmember Spectral Mixture Analysis (MESMA) was applied to AVIRIS data to estimate green vegetation (GV), non-photosynthetic vegetation (NPV) and soil fractions in crop fields each year. MESMA and crop reports (R2 = 0.9) showed that soil (i.e.; non-cultivated areas) increased during the summers of the drought; with the smallest GV area in 2015, the second year classified with exceptional drought in this period. According to MESMA, 34 % of the cropland was covered by GV in 2015, and 69.5·104 ha according to the crop reports. MESMA also registered the highest value of soil area in 2015 (48 %). The year with most cultivated area was 2017, the wettest year in the studied period, with 54 % of the croplands covered by GV and 75.2·104 ha. This study verified that the non-cultivated areas increased in the Central Valley during the exceptional drought period and validated the use of AVIRIS imagery to monitor broad-scale cropland use changes in future climatic extreme events.

Drought impacts to water footprints and virtual water transfers of the Central Valley of California

American Geophysical Union (AGU) | June 23rd, 2017

Drought intensity and duration interact to magnify losses in primary productivity

American Association for the Advancement of Science (AAAS) | October 16th, 2025

As droughts become longer and more intense, impacts on terrestrial primary productivity are expected to increase progressively. Yet, some ecosystems appear to acclimate t

As droughts become longer and more intense, impacts on terrestrial primary productivity are expected to increase progressively. Yet, some ecosystems appear to acclimate to multiyear drought, with constant or diminishing reductions in productivity as drought duration increases. We quantified the combined effects of drought duration and intensity on aboveground productivity in 74 grasslands and shrublands distributed globally. Ecosystem acclimation with multiyear drought was observed overall, except when droughts were extreme (i.e., ≤1-in-100-year likelihood of occurrence). Productivity losses after four consecutive years of extreme drought increased by ~2.5-fold compared with those of the first year. These results portend a foundational shift in ecosystem behavior if drought duration and intensity increase, from maintenance of reduced functioning over time to progressive and profound losses of productivity when droughts are extreme.