Using an integrated hydrological model to estimate the usefulness of meteorological drought indices in a changing climate

Abstract

Abstract. Droughts are serious natural hazards, especially in semi-arid regions. They are also difficult to characterize. Various summary metrics representing the dryness level, denoted drought indices, have been developed to quantify droughts. They typically lump meteorological variables and can thus directly be computed from the outputs of regional climate models in climate-change assessments. While it is generally accepted that drought risks in semi-arid climates will increase in the future, quantifying this increase using climate model outputs is a complex process that depends on the choice and the accuracy of the drought indices, among other factors. In this study, we compare seven meteorological drought indices that are commonly used to predict future droughts. Our goal is to assess the reliability of these indices to predict hydrological impacts of droughts under changing climatic conditions at the annual timescale. We simulate the hydrological responses of a small catchment in northern Spain to droughts in present and future climate, using an integrated hydrological model calibrated for different irrigation scenarios. We compute the correlation of meteorological drought indices with the simulated hydrological time series (discharge, groundwater levels, and water deficit) and compare changes in the relationships between hydrological variables and drought indices. While correlation coefficients linked with a specific drought index are similar for all tested land uses and climates, the relationship between drought indices and hydrological variables often differs between present and future climate. Drought indices based solely on precipitation often underestimate the hydrological impacts of future droughts, while drought indices that additionally include potential evapotranspiration sometimes overestimate the drought effects. In this study, the drought indices with the smallest bias were the rainfall anomaly index, the reconnaissance drought index, and the standardized precipitation evapotranspiration index. However, the efficiency of these drought indices depends on the hydrological variable of interest and the irrigation scenario. We conclude that meteorological drought indices are able to identify years with restricted water availability in present and future climate. However, these indices are not capable of estimating the severity of hydrological impacts of droughts in future climate. A well-calibrated hydrological model is necessary in this respect.

Impact of climate change on meteorological, hydrological and agricultural droughts in the Lower Mekong River Basin: a case study of the Srepok Basin, Vietnam

“…For instance, Wang et al () investigated the potential impacts of climate change on meteorological, agricultural and hydrological droughts in The Salt Creek Catchment (US) and revealed an increase in drought frequency in the future; Leng et al () conducted the similar study in China and pointed out that droughts will become more extreme and frequent under climate change scenarios. Moreover, von Gunten et al () used drought indices and the HydroGeoSphere hydrological model to project hydrological impacts of droughts in the context of climate change in the Lerma catchment (Spain) and indicated an increase in drought severity in the future. In another study, Kamali et al () assessed meteorological, agricultural and hydrological droughts in the Karkheh River Basin (Iran) using three drought indices and Soil and Water Assessment Tool (SWAT) and found that the frequency of extreme droughts is predicted to increase in the future.…”

Spatial Multi-Criterion Decision Making (SMDM) Drought Assessment and Sustainability over East Africa from 1982 to 2015

“…Droughts are considered a serious natural hazard, especially in semi-arid regions where devastating and catastrophic damages are recorded [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], and have been mainly categorized (on the basis of duration, impact and recovery rate) into meteorological (defined by a lack of precipitation over a certain period of time for a certain region), agricultural (defined by a period of declining soil moisture and reduced crop yields) and hydrological (defined by a reduced surface and subsurface water availability for a given water resource), and socio-economic drought, expressed to mean "a failure of water resource management to meet the supply and demand of water, taken as an economic good" [16][17][18][19]. The socio-economic definition of drought is a perspective that has not been applied to many studies/analyses of drought found in the literature as it is possibly seen as an outcome/impact of drought rather than a category of drought.…”