![]() In coastal communities, groundwater pumping can reverse natural flows to the ocean, allowing seawater to enter the aquifer system (known as saltwater intrusion). This can lead to subsidence (sinking of the ground), permanent loss of storage for groundwater, and infrastructure damage. Increased groundwater pumping to meet water demand during drought can lead to aquifer depletion. The Standardized Precipitation Index, a probability index that considers only precipitation, is computed for several timescales ranging from 1 to 72 months to capture the various scales of both short-term and long-term drought.The Palmer Z-Index measures short-term drought on a monthly scale.The Crop Moisture Index measures short-term drought on a weekly scale and is used to quantify drought's impacts on agriculture during the growing season.The Palmer indices-water balance indices that consider water supply (precipitation), demand (evapotranspiration), and loss (runoff)-for short-term drought include the following: Indices used to monitor short-term drought-related impacts (timescales ranging from a few days to a few months) include wildfire danger, non-irrigated agriculture, topsoil moisture, range and pasture conditions, and unregulated streamflows. The prediction of flash droughts on subseasonal timescales is of critical importance for impact assessment, disaster mitigation, and loss prevention. Closely monitoring rapid changes in ET, along with soil moisture and precipitation conditions, can provide early warnings of flash drought development. Flash droughts occur more often than perceived and can cause major agricultural losses if they are not predicted and detected in a timely manner. In contrast with conventional drought, which is mainly driven by lack of precipitation, flash drought usually includes abnormally high temperatures, winds, and/or incoming radiation that leads to abnormally high evapotranspiration (ET) rates. In its simplest form, flash drought is the rapid onset of drought. However, some animals, including birds, obtain water from the food they eat and may not be initially impacted in short-term drought by reductions in available water. Harm to plants caused by drought has cascading effects throughout ecosystems. Short-term drought also causes woody plants such as trees and shrubs to wilt, their leaves to turn brown, and some leaves to drop away from plants ( UMass Amherst). Combined with heat and wind, low soil moisture can harm agricultural crops in a relatively short period of time if they are not able to access other water supplies. ![]() Agricultural and Ecological ImpactsÄuring short-term drought, topsoil moisture becomes depleted, which impacts shallow-rooted plants such as grasses-including corn and wheat crops-first because their roots cannot reach deep enough into the soil to access other water sources. If water is pumped at a faster rate than the underlying aquifer is recharged from precipitation or other sources, water levels can drop, resulting in decreased water availability and deterioration of groundwater quality. However, groundwater use often increases during drought from increased pumping to meet water demands. In contrast, it may take a year or more before levels in wells (reflecting groundwater levels) reflect a shortage of rainfall. During short-term drought, declines in surface water flows can impact water supplies for agriculture, drinking water, hydropower production, navigation, recreation, and ecosystem habitats.
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