Aridity and Drought
GDrought is a prolonged period of abnormally low precipitation that can lead to water shortages, impacting ecosystems, agriculture, water supply, and various human activities. It is a complex natural hazard with significant environmental, social, and economic consequences. Here are key aspects of drought:
Types of Drought
Depending on the variables used to characterize it and the systems or sectors being impacted, drought may be classified in different types, such as
- Meteorological drought: Lack of rainfall or below-average precipitation for an extended period characterizes meteorological drought. This is the most common form of drought.
- Hydrological drought: Hydrological drought refers to water shortage in streams or storages such as reservoirs, lakes, lagoons, and groundwater which usually occurs due to prolonged dry conditions.
- Agricultural and ecological drought: Agricultural drought relates to soil moisture deficits that affect crop growth. It occurs when there's not enough water in the soil to meet the needs of crops.
Impacts of Drought
Drought has extensive impacts across multiple sectors, affecting ecosystems, agriculture, water resources, energy production, commerce, public health, and infrastructure stability[1].
- Ecosystems and Biodiversity: Changes in soil moisture and surface water can alter the rate of carbon uptake by ecosystems, affecting the carbon cycle and overall ecosystem health. They also alter suitable climate zones for wild species, potentially leading to habitat loss and changes in species distributions. The altered conditions can increase can increase the prevalence of pests and pathogen-carrying vectors. Prolonged dry conditions increase the risk of wildfires, as vegetation becomes more susceptible to ignition.
- Agriculture: Reduction in water availability challenges the water supplies needed for irrigation, affecting crop yields. Insufficient water can stress crops and forests, affecting crop quality. Severe water stress can lead to crop failure, especially during key developmental stages or extended drought periods. Drought can also contribute to insect outbreaks, increases in wildfire, and altered rates of carbon, nutrient, and water cycling—impacting agricultural production.
- Power and Energy (copied from drought.gov) Production of all types of energy, including electricity, requires water. Because the energy sector is dependent on water availability, drought can severely impact energy systems.
- Thermoelectric electricity generation. Thermoelectric power plants use steam turbines to generate electricity using a variety of fuel sources. Large amounts of water are needed to generate steam and for cooling. Drought conditions can result in reduced plant efficiency and generation capacity and can also impact the supply chain for coal, natural gas, biofuel, and nuclear fuel.
- Hydroelectric power generation. Hydroelectric power is generated by funneling water through power plants contained in dam structures. When water levels in reservoirs become low, the force of water pressure required to turn hydro turbine blades is reduced, which affects productivity.
- Hydraulic fracturing and refining. Reduced water availability affects the production and refining of petroleum and natural gas. During droughts, hydraulic fracturing (or fracking) and fuel refining operations can require alternative water supplies or may be forced to temporarily shut down. Shutdowns can increase costs, which in turn can raise consumer prices.
- Biofuels. Reduced water availability and decreased soil moisture during drought can reduce the cultivation of biofuel feedstocks.
- Manufacturing: Manufacturers use water for many processes, including fabrication, washing, cooling, and transporting goods. Water is also often incorporated into products themselves. Reductions in the amount of available water can reduce manufacturing productivity or even lead to temporary closures of key manufacturing facilities.
- Navigation and Transportation Drought impacts port and waterway transportation and supply chains, resulting in increased transportation costs. Higher temperatures that often coexist with drought can impact roads, airport runways, and rail lines.
- Recreation and Tourism Drought impacts various water-dependent activities like boating and skiing, leading to reduced revenues in tourism and recreation sectors. Increased wildfire risk during droughts further affects tourism by limiting access and deterring visitors due to safety concerns. Additionally, degraded water resources from drought can lower water quality and reduce streamflow, impacting hunting and fishing opportunities.
- Public health Drought increases disease infection rates. Low flow volume and higher stream temperature during drought can lead to reduced dissolved oxygen, and more concentrated pollutants, posing health risks for human and aquatic life.
- Water Utilities Drought can result in impacts to water utility operations, including:
- Loss of water pressure and water supply
- Poor water quality from the source that may require additional treatment to meet drinking water standards
- Inability to access alternative and supplementary water sources because of high demand by and competition from other users
- Increased customer demand
- Increased costs and reduced revenues related to responding to drought impacts.
- Infrastructure The alternation of dry and wet spells can lead to swelling and shrinkage of clay soils, causing structural damage to buildings.
Observed and Projected changes in Drought (TBA)
or called "How does CO2 increase impact drought"
Droughts are often analyzed using indices that are measures of drought severity, duration and frequency . There are many drought indices published in the scientific literature. Below are some metrics and indices used in regional assessments on droughts. They are subdivided into the three drought categories listed above.[2]
Indices for meteorological drought
| Indices | Brief Introduction | Data Access | Recommendation Rating |
| Consecutive Dry Days (CDD) |
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| Standardized Precipitation Index (SPI) | |||
| Standardized Precipitation Index Accumulated over 6 months (SPI-6) |
Indices for hydrological drought
| Indices | Brief Introduction | Data Access | Recommendation Rating |
| extreme low runoff |
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| low flow days | |||
| Standardized runoff index (SRI) | |||
| Standardized streamflow index (SSI) |
Indices for agricultural and ecological drought
| Indices | Brief Introduction | Data Access | Recommendation Rating |
| Palmer drought severity index (PDSI) | PDSI is a regional drought index commonly used for measuring the severity of drought conditions. It is a standardized index that ranges from -10 (dry) to +10 (wet), with >4 indicating extreme wet conditions and <-4 indicating extreme dry conditions.[3]
Self-calculating PDSI is not easy, as a multitude of computation is involved. Some open-source code is available online. Here is one from Jacobi et al. (2013)[4](see "Supporting Information" for the code). |
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| Standardized precipitation evapotranspiration index (SPEI) | SPEI serves as a comprehensive drought index due to its multi-scalar nature, accommodating diverse scientific disciplines for detecting, monitoring, and analyzing droughts. SPEI assesses drought severity based on intensity and duration, identifying onset and cessation of drought episodes. Its versatility allows for comparative analysis across different climates and over time.[5] |
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| Soil Moisture (total and surface) | |||
| Evaporative Demand Drought Index (EDDI) | |||
| Soil Moisture Anomalies (SMA) | |||
| Standardized soil moisture index (SSMI) |
Other resources
The US Drought monitor
The US Drought Monitor (USDM) is a comprehensive and collaborative effort by several federal agencies, including the National Drought Mitigation Center (NDMC), the United States Department of Agriculture (USDA), and the National Oceanic and Atmospheric Administration (NOAA), among others. It provides up-to-date information and assessment of drought conditions across the United States.
Link for the US Drought Monitor Map (November 2023): https://droughtmonitor.unl.edu/Maps/MapArchive.aspx
Dataset can be accessed here: https://docs.google.com/spreadsheets/d/1k1YhIULXMt4URSIpeJfgfRbiee_YA7oXfl2_s6xfnpk/edit?usp=drive_link
National Integrated Drought Information System
The National Oceanic and Atmospheric Administration’s (NOAA's) National Integrated Drought Information System (NIDIS) program is an integrated information system that coordinates drought monitoring, forecasting, planning, and information at federal, tribal, state, and local levels across the country.
Notes
(Notes from Xiaojuan: List the sectors impacted by drought and create separate page for each sector; the webpage should be information on what and how climate hazards impact the sector
Reference
1. https://climatedata.imf.org/
2. https://yaleclimateconnections.org/2021/06/california-americas-garden-is-drying-out/
- ↑ https://www.drought.gov/sectors/
- ↑ (Table 11.3 in IPCC WG1 Ch11.9)
- ↑ Dai, Aiguo & National Center for Atmospheric Research Staff (Eds). Last modified 2023-08-19 "The Climate Data Guide: Palmer Drought Severity Index (PDSI).” Retrieved from https://climatedataguide.ucar.edu/climate-data/palmer-drought-severity-index-pdsi on 2024-07-17.
- ↑ https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/wrcr.20342
- ↑ https://spei.csic.es/home.html