Hydrological drought persistence and recovery over the CONUS: A multi-stage framework considering water quantity and quality

Drought impact on pharmaceuticals in surface waters in Europe: Case study for the Rhine and Elbe basins

Hydrological droughts are expected to increase in frequency and severity in many regions due to climate change. Over the last two decades, several droughts occurred in Europe, including the 2018-drought, which showed major adverse impacts for nature and different sectoral uses (e.g. irrigation, drinking water). While drought impacts on water quantity are well studied, little understanding exists on the impacts on water quality, particularly regarding pharmaceutical concentrations in surface waters. This study investigates the impact of the 2018-drought on concentrations of four selected pharmaceuticals (carbamazepine, sulfamethoxazole, diclofenac and metoprolol) in surface waters in Europe, with a major focus on the Elbe and Rhine rivers. Monitoring data were analysed for the period of 2010-2020 to estimate the spatiotemporal patterns of pharmaceuticals and assess the concentration responses in rivers during the 2018-drought compared to reference years. Our results indicate an overall deterioration in water quality, which can be attributed to the extremely low flow and higher water temperatures (∼ + 1.5 °C and + 2.0 °C in Elbe and Rhine, respectively) during the 2018-drought. Our results show an increase in the concentrations of carbamazepine, sulfamethoxazole, and metoprolol, but reduced concentrations of diclofenac during the 2018-drought. Significant increases in carbamazepine concentrations (+45 %) were observed at 3/6 monitoring stations in the upstream part of the Elbe, which was mainly attributed to less dilution of chemical loads from wastewater treatment plants under drought conditions. However, reduced diclofenac concentrations could be attributed to increased degradation processes under higher water temperatures (R2 = 0.60). Moreover, the rainfed-dominated Elbe exhibited more severe water quality deterioration than the snowmelt-dominated Rhine river, as the Elbe's reduction in dilution capacity was larger. Our findings highlight the need to account for the impacts of climate change and associated increases in droughts in water quality management plans, to improve the provision of water of good quality for ecosystems and sectoral needs.

Dynamics of dissolved organic carbon during drought and flood events: A phase-by-stages perspective

Dissolved organic carbon (DOC) is a key water quality parameter that plays a crucial role in controlling aquatic ecosystems and carbon cycling. Understanding DOC dynamics during hydrological extremes (i.e., droughts and floods) helps in managing water quality, but such variability is rarely studied. Furthermore, how differences in DOC concentrations among phase-by-stages of drought/flood affect simulation performances based on hydrological features remains unclear. Here, phase-by-stages of hydrological drought (flood) were divided into intensification (rising) and recovery (falling) periods based on drought peak intensity (flood peak intensity). The long-term (1976-2019) daily discharge and weekly (biweekly) DOC concentrations from four headwater streams with different watershed sizes (from 9.97 to 119.09 ha) in south-central Ontario, Canada, were used to achieve the above aims. The results showed that (i) the average DOC concentration during intensification (rising) stage of drought (flood) was smaller (larger) than during recovery (falling). (ii) Simulations performed better when accounting for phase-by-stages of drought/flood, with reductions in mean absolute percentage error of 32.85 % and 53.59 % for drought and flood events, respectively. These results will help understand the dynamics of DOC during hydrological extremes and improve simulation performance of numerical models for water quality parameters under changing environmental conditions.

Agricultural Disaster Risk Management and Capability Assessment Using Big Data Analytics

Besides many impacts, climate change and the rise of harsh weather have a huge hit that jeopardizes agricultural sectors. Natural catastrophes, including flooding and wildfires, are the sources of significant declines in crop production. National governments make an essential commitment, and foreign institutions work together to mitigate disasters' resilience vulnerability. These hazards have pushed catastrophe management to the forefront and made it an expanding scholarly area of study. The remarkable growth of information technology has motivated the scientific group to integrate this technology into emergency management. In this article, agricultural disaster risk management (ADRM) is offered to decide the status quo of the research on agriculture disaster management and the significance of big data. This article's primary objective is to provide technical metric analysis to analyze the body of research carried out in the past decade on different forms of disasters and the use of significant volumes. For the data assessment, the annual growth of publication outcomes, the corresponding categories of topics, and the productivity study specifications was determined. The flux of raw and analytical data from comprehensive data is so established that another effect is heavily affected in the final performance of forecasting. The assessment of ADRM proposed would have been based on data provided by the Department of Indian Meteorology, and improvement is illustrated in incorporating the mechanism proposed in flood prediction long before the occurrence of floods.

Climate-catchment-soil control on hydrological droughts in peninsular India

Most land surface system models and observational assessments ignore detailed soil characteristics while describing the drought attributes such as growth, duration, recovery, and the termination rate of the event. With the national-scale digital soil maps available for India, we assessed the climate-catchment-soil nexus using daily observed streamflow records from 98 sites in tropical rain-dominated catchments of peninsular India (8–25° N, 72–86° E). Results indicated that climate-catchment-soil properties may control hydrological drought attributes to the tune of 14–70%. While terrain features are dominant drivers for drought growth, contributing around 50% variability, soil attributes contribute ~ 71.5% variability in drought duration. Finally, soil and climatic factors together control the resilience and termination rate. The most relevant climate characteristics are potential evapotranspiration, soil moisture, rainfall, and temperature; temperature and soil moisture are dominant controls for streamflow drought resilience. Among different soil properties, soil organic carbon (SOC) stock could resist drought propagation, despite low-carbon soils across the Indian subcontinent. The findings highlight the need for accounting feedback among climate, soil, and topographical properties in catchment-scale drought propagations.

Dissolved organic carbon response to hydrological drought characteristics: Based on long-term measurements of headwater streams

Influence of extreme hydrological events on water quality has been widely concerned. For instance, droughts can inhibit dissolved organic carbon (DOC) exports or imports. However, the response relationship of DOC to hydrological drought characteristics (i.e., duration and severity) requires more in-depth research. We propose an integrated framework for constructing, validating, and applying the response relationship model, and investigate the capability of response model to simulate DOC based on hydrological drought characteristics. Three headwater basins (HP3a, HP4, and HP6), with different drainage areas (9.28-122.80 ha) and long-term (>40 year) observed DOC concentration and hydrometeorological data, in Harp Lake catchment, south-central Ontario, southeastern Canada, are used to demonstrate the proposed framework. Run theory and variable drought thresholds (VDTs) are used to identify hydrological drought characteristics, and DOC during hydrological drought is extracted. Based on the extracted hydrological drought characteristics and DOC for one basin (i.e., HP3a), the response relationship model is constructed and validated, and then applied to other two basins (i.e., HP4 and HP6). Three evaluation indicators: coefficient of determination (R²), root-mean-square-error (RMSE), and mean absolute percentage error (MAPE), are served to test the goodness-of-fit performance of the response relationship model. The results show that (i) annual DOC concentration showed a significant (a = 0.01) increasing trend during 1978-2018 in the study basin. (ii) During the hydrological drought, the variation of temperature affected DOC variation indirectly through direct influence on SO₄ variation. (iii) The response sensitivity of DOC to hydrologic process with different timescales is varying within a year, namely, there is a larger response sensitivity from March to May than in other months. (iv) DOC during the hydrological drought has a close and regular linear relationship with hydrological drought characteristics, i.e., with the increase of drought duration and severity, DOC concentration also increases. The relationship with drought duration is better than that of severity (R² = 0.92 vs 0.35). (v) The response relationship model (autoregressive integrated moving average) can simulate DOC in hydrological drought (R² ≥ 0.87, RMSE ≤ 0.86, MAPE ≤ 13.69%) at HP3a, and also has good applications at HP4 and HP6 basins. These results provide an improved understanding of DOC-drought relationship, and may support policy makers that look for increased resilience of aquatic ecological security to droughts.

Spatial heterogeneity of changes in cropland ecosystem water use efficiency and responses to drought in China

Understanding cropland ecosystem water use efficiency (eWUE) responses to drought is important for sustainable water resource management and food security. Today in China, the spatiotemporal patterns of eWUE and responses to drought across different cropland classes remain poorly quantified. In this study, we characterized the spatial temporal variability in cropland eWUE and response to drought in China from 1982 to 2017 using the satellite-retrieved evapotranspiration (ET), gross primary production (GPP), and self-calibrating Palmer Drought Severity Index (scPDSI), in conjunction with the Global Food Security-support Analysis Data product for Crop Dominance (GFSAD1KCD) data. Results indicated that (1) mean annual cropland eWUE had a spatial range from 0 to 9.94 g C kg-1 H2O, with higher values (2.06 g C kg-1 H2O) in class 4 (rainfed: wheat, rice, and soybeans dominant), whereas the lowest eWUE (1.58 g C kg-1 H2O) occurred in class 2 (irrigated mixed crop 1: wheat, rice, barley, and soybeans). (2) Annual eWUE, GPP, and ET values for croplands in China increased significantly between 1982 and 2017. Class 1 (irrigated wheat and rice) had the highest trend of 0.011 g C kg-1 H2O yr-1, and class 6 (rainfed: corn and soybeans) had the lowest of 0.0007 g C kg-1 H2O yr-1. Apart from class 4, annual GPP and ET were enhanced in most cropland classes from 1982 to 2017 (p<0.01). (3) Rainfed croplands generally had higher eWUE, GPP, and ET values than irrigated croplands. Except for rainfed cropland eWUE, all other cropland variables increased significantly (p<0.001) from 1982 to 2017. (4) Correlation analysis found that the 19.66% (15.62%) of cropland had significant negative (positive) correlations between eWUE and current-year scPDSI. The legacy effects of drought on cropland eWUE indicated that previous and current-year drought impacts on cropland eWUE were in the same direction. Our results provide insights into variability in cropland eWUE and its response to drought in China, where there is a growing demand for agricultural water resource management.

The Role of Large Dams in a Transboundary Drought Management Co-Operation Framework—Case Study of the Kabul River Basin

Hydrologic drought is a frequent phenomenon in the transboundary Kabul River Basin (KRB), the vital resource shared between the two nations of Afghanistan and Pakistan. While the KRB has vast water resources, these resources are subject to extreme hydrologic events and, as a result, are not adequately managed to deal with the stress during drought conditions in the transboundary setting with no formal agreement or treaty. Rapid population growth and increases in agricultural land will require balanced water distribution to meet the array of needs. The Soil and Water Assessment Tool (SWAT) is used to evaluate distribution options for flow frequencies under existing and proposed large dams in the headwaters of the KRB. The calibrated SWAT streamflow results are employed for statistical analyses of the Standardized Streamflow Index (SSI) and Annual Cumulative Deficit Volume (ACDV) to investigate hydrologic drought time series and identify the role of proposed dams to be used for drought mitigation. Based on the SSI, proposed dams can provide additional storage that will partially address hydrologic droughts in the future. At the same time, restrictions on agricultural land expansion and water intakes are other measures to facilitate balanced water resource availability. This study discusses the intricacies of transboundary conflict and cooperation, water rights, and drought risk management; as well, recommendations for a KRB transboundary Drought Task Force (DTF) between Afghanistan and Pakistan are provided, to develop a science-based policy for using the stored waters in large dams for drought relief, fairly and transparency.

Drought Events over the Amazon River Basin (1993–2019) as Detected by the Climate-Driven Total Water Storage Change

The Gravity Recovery and Climate Experiment (GRACE) mission has measured total water storage change (TWSC) and interpreted drought patterns in an unparalleled way since 2002. Nevertheless, there are few sources that can be used to understand drought patterns prior to the GRACE era. In this study, we extended the gridded GRACE TWSC to 1993 by combining principal component analysis (PCA), least square (LS) fitting, and multiple linear regression (MLR) methods using climate variables as input drivers. We used the extended (climate-driven) TWSC to interpret drought patterns (1993–2019) over the Amazon basin. Results showed that, in the Amazon area with the resolution of 0.5°, GRACE, GRACE follow on, and Swarm had correlation coefficients of 0.95, 0.92, and 0.77 compared with climate-driven TWSCS, respectively. The drought patterns assessed by the climate-driven TWSC were consistent with those interpreted by the Palmer Drought Severity Index and GRACE TWSC. We also found that the 1998 and 2016 drought events in the Amazon, both induced by strong El Niño events, showed similar drought patterns. This study provides a new perspective for interpreting long-term drought patterns prior to the GRACE period.

Small Floodplain Reservoirs in the Face of Climate Change—Sink or Source of Nutrients?

Despite various water protection measures, good water quality and reduction of nutrient loads seem very distant goals, largely due to limited knowledge of processes occurring in river valleys. Our study aimed at establishing the role of small floodplain reservoirs in the eutrophication processes, in the face of recent climate changes. The content of phosphorus and nitrogen compounds was determined in sediments and water of small floodplain reservoirs, (the Vistula River Valley, Poland) using spectrophotometric and Kjeldahl’s method. Nutrient loads in sediments were linked to the texture and total organic carbon content. Seasonal changes in water quality were strictly connected to changing weather conditions, flood and drought. The concentrations of PO43− and NO3− were found to rise after summer flooding. Increases in NH4+, total phosphorus (TP) and total nitrogen (TN) were correlated with the surface water area reduction in the reservoirs, which during the year of the study was on average 62%. Therefore, small floodplain reservoirs could be considered simultaneously as sinks and sources of nutrients. On the one hand, they accumulate P and N compounds carried by the river during the flood. On the other hand, climate change cause that small floodplain reservoirs may be responsible for enhanced biomass production.

Carbon footprint and water footprint in China: Similarities and differences

Water crisis and carbon emissions are the biggest challenges facing China's environment. International trade has exacerbated the pressures of China's carbon emissions and water consumption. This work establishes a multi-regional input-output model for time series analysis. It aims to understand how human final demands affect an economy's water consumption and carbon emissions by contrasting the similarity and dissimilarity of China's carbon footprint and water footprint. The results show that >90% of China's carbon and water footprints are embodied in trade, and China was a net exporter of embodied carbon and virtual water from 1990 to 2010. This could mean that China is burdened with more environmental pollution and resource pressures in the global supply and demand chain. We find that China's main net export destination of carbon-water-intensive products are developed areas such as North America and Europe, while China's main net import sources are developing areas such as Africa and Southeast Asia. Heavy industry and transportation contain the most carbon footprint in China, while agriculture, fishery and light industry contain the most water footprint. Also, China's embodied carbon and virtual water in diverse sectors in different years vary from region to region. The similarities and differences between China's carbon and water footprints should be considered when making decisions to better governance of climate change and water crisis.

Drought Vulnerability in the United States: An Integrated Assessment

Droughts are among the costliest natural hazards in the U.S. and globally. The severity of the hazard is closely related to a region’s ability to cope and recover from the event, an ability that depends on the region’s sensitivity and adaptive capacity. Here, the vulnerability to drought of each state within the contiguous U.S. is assessed as a function of exposure, sensitivity, and adaptive capacity, using socio-economic, climatic, and environmental indicators. The division of vulnerability into three sub-indices allows for an assessment of the driver(s) of vulnerability of a state and as such provides a foundation for drought mitigation and planning efforts. In addition, a probabilistic approach is used to investigate the sensitivity of vulnerability to the weighting scheme of indicators. The resulting geographic distribution of relative vulnerability of the states is partially a reflection of their heterogeneous climates but also highlights the importance of sustainable adaptation of the local economy to water availability in order to reduce sensitivity and to limit the impact of drought. As such, the study at hand offers insights to local and regional planners on how to effectively distribute funds and plan accordingly in order to reduce state-level drought vulnerability today and in the future.

Assessing Meteorological and Agricultural Drought in Chitral Kabul River Basin Using Multiple Drought Indices

Drought is a complex and poorly understood natural hazard in complex terrain and plains lie in foothills of Hindukush-Himalaya-Karakoram region of Central and South Asia. Few research studied climate change scenarios in the transboundary Chitral Kabul River Basin (CKRB) despite its vulnerability to global warming and importance as a region inhabited with more than 10 million people where no treaty on use of water exists between Afghanistan and Pakistan. This study examines the meteorological and agricultural drought between 2000 and 2018 and their future trends from 2020 to 2030 in the CKRB. To study meteorological and agricultural drought comprehensively, various single drought indices such as Precipitation Condition Index (PCI), Temperature Condition Index (TCI), Soil Moisture Condition Index (SMCI) and Vegetation Condition Index (VCI), and combined drought indices such as Scaled Drought Condition Index (SDCI) and Microwave Integrated Drought Index (MIDI) were utilized. As non-microwave data were used in MIDI, this index was given a new name as Non-Microwave Integrated Drought Index (NMIDI). Our research has found that 2000 was the driest year in the monsoon season followed by 2004 that experienced both meteorological and agricultural drought between 2000 and 2018. Results also indicate that though there exists spatial variation in the agricultural and meteorological drought, but temporally there has been a decreasing trend observed from 2000 to 2018 for both types of droughts. This trend is projected to continue in the future drought projections between 2020 and 2030. The overall study results indicate that drought can be properly assessed by integration of different data sources and therefore management plans can be developed to address the risk and signing new treaties.

Assessing the potential effect of extreme weather on water quality and disinfection by-product formation using laboratory simulation

Increased frequency and severity of extreme weather events (i.e., floods and droughts) combined with higher temperatures can threaten surface water quality and downstream drinking water production. This study characterized the effects of extreme weather events on dissolved organic matter (DOM) washout from watershed soils and the corresponding contribution to disinfection by-product (DBP) precursors under simulated weather conditions. A laboratory simulation was performed to assess the effects of temperature, drought, rainfall intensity, sea level rise, and acid deposition on the amount of DOM released from soil samples. DBP formation potentials (DBPFPs) were obtained to assess the effect of extreme weather events on DBP formation and drinking water quality. The results demonstrated that the dissolved organic carbon (DOC) and carbonaceous DBP levels increased with increasing temperature in a dry (drought) scenario. Regardless of the watershed from which a soil sample was obtained and the incubation temperature during rewetting or chlorination processes, the DOC and carbonaceous DBP levels also increased with increasing temperature. Brominated DBP formation was increased when bromide was present during the rewetting of soil, indicating the effect of sea level rise. When bromide was present during the chlorination of water for DBPFP tests, only the level of brominated DBPs increased. Acid deposition had various effects under different weather conditions. The results of heavy rainfall simulations suggested that water quality deteriorates at the beginning of an extreme rainfall event. Abundant DOM was washed out of soil, leading to a peak in the DBPFP level. The level of DOM in seepage water was less than that of the surface runoff water during rainfall. The situation was more severe when the rainfall came after a long drought and the drought-rewetting cycle effect occurred.

Temporal and spatial variations in water discharge and sediment load on the Loess Plateau, China: A high-density study

Over the past 50 years, a series of soil and water conservation measures have been implemented on the Loess Plateau, including biological, engineering, and agricultural measures. As a result, water discharge and sediment load on the plateau have undergone significant changes. In this study, we compared the water discharge and sediment load at >100 hydrological stations across the Loess Plateau during the period 2008-2016 (P2) with the water discharge and sediment load during the period 1971-1987 (P1), and detected the main sources of sediment in each of the two periods. We then performed an attribution analysis to quantify the influence of different factors on the changes in sediment load. We found the following results: (1) Water discharge was reduced by 22% in P2 compared with P1, whereas the sediment load was reduced by 74%. (2) Sediment resources are mainly concentrated between Toudaoguai and Tongguan stations: this region contributed >88% of the total sediment load at the terminal station (Huayuankou station) in both P1 and P2. (3) When considering only the changes in sediment concentration on the Loess Plateau, we conclude that the contribution of human activities was >72%. This study provides a detailed description of the temporal and spatial variations in water and sediment across the Loess Plateau, providing a reliable reference for the future development of ecological soil and water conservation measures on the Loess Plateau.

Remote Sensing of Water Use Efficiency and Terrestrial Drought Recovery across the Contiguous United States

Ecosystem water-use efficiency (WUE) is defined as the ratio of carbon gain (i.e., gross primary productivity; GPP) to water consumption (i.e., evapotranspiration; ET). WUE is markedly influential on carbon and water cycles, both of which are fundamental for ecosystem state, climate and the environment. Drought can affect WUE, subsequently disturbing the composition and functionality of terrestrial ecosystems. In this study, the impacts of drought on WUE and its components (i.e., GPP and ET) are assessed across the Contiguous US (CONUS) at fine spatial and temporal resolutions. Soil moisture simulations from land surface modeling are utilized to detect and characterize agricultural drought episodes and remotely sensed GPP and ET are retrieved from the moderate resolution imaging spectroradiometer (MODIS). GPP, as the biome vitality indicator against drought stress, is employed to investigate drought recovery and the ecosystems’ required time to revert to pre-drought condition. Results show that drought recovery duration indicates a positive correlation with drought severity and duration, meaning that a protracted drought recovery is more likely to happen following severe droughts with prolonged duration. WUE is found to almost always increase in response to severe (or worse) drought episodes. Additionally, ET anomalies are negatively correlated with drought severity and ET is expected to decrease during severe (or worse) drought episodes. Lastly, the changes of WUE are decomposed in relation to its components and the cross-relation among the variables is revealed and a consistent changing pattern is detected.