Assessing Temporal Drought Severity in Kenya's Arid and Semi‐Arid Landscape Using Google Earth Engine and the Normalised Difference Drought Index

Accurately characterizing the response of Gross Primary Production (GPP) and plant transpiration to soil moisture stress is crucial for reliable climate simulations as we expect an increase in drought events. In this study, we used the ORCHIDEE land surface model to investigate how the physiological response of vegetation to soil moisture stress can be refined, focusing on Europe, which has experienced significant droughts. We used in situ GPP and latent heat flux (LE) data from more than 40 sites across various biomes, along with data assimilation techniques, to improve GPP and plant transpiration representations. This work shows that the speed of stomatal closure under soil moisture stress can be refined by incorporating vegetation acclimation to long‐term vapor pressure deficit (VPD) conditions. This new drought response results in a greater reduction in GPP root mean square deviation than a response based solely on biome type, achieving an 18% improvement at the site scale, whereas the biome‐type‐only version shows no improvement. Then, the two model versions show similar performance in simulating LE, with an 8%–9% improvement at the site scale. Projections up to 2100 show that, over Europe, incorporating VPD acclimation results in a vegetation sensitivity to drought with stomatal closure that is 22% lower than a response that only depends on the vegetation type. This study underscores the importance of better understanding and accounting for potential acclimation mechanisms in vegetation response to climate change and extreme events.

As a natural disaster, drought affects many sectors such as agriculture and hydrology, as well as having an effect on air quality. In terms of air pollution, drought can reduce wet scavenging of pollutants and change their chemical production/loss and lifetime. This study investigates the relationship between drought events and air pollutants in Turkey. As a drought indicator, the Standardized Precipitation‐Evapotranspiration Index (SPEI)‐1 monthly values for dry (SPEI < −0.99), normal (−0.99 < SPEI < 0.99) and wet (SPEI < 0.99) conditions were used to investigate the changes in PM10, PM2.5, O3 concentration levels. Monthly mean PM10 values of 80 stations for the period 2010–2018, PM2.5 and O3 values of 10 and 12 stations, respectively, were used for the analysis throughout the 2014–2018 period. According to the results, while frequency occurrence of normal conditions decreased in the last period (2010–2018) when compared to the first (1901–2009), drought conditions have significantly increased in each region of Turkey in the last decade. Highest increase in drought events occurred in the inner/southern parts of Turkey. In dry events, while PM10 levels of the stations show above‐normal values, highest regional increase in PM10 was found in the Central Anatolia (CAR), Mediterranean (MeR), Aegean (AR) and Marmara (MR) regions of the country. In fall, high daily temperatures and cloudless days in CAR and MeR regions are seen under deep surface low over continental Europe and surface high over Caspian Sea, which result in severe dryness events and associated high PM10 values in the air quality stations. On the other hand, as a consequence of the expanding Asiatic monsoon low to the eastern part of Turkey, significant amount of moisture is transferred from the Eastern Mediterranean Sea surface to the CAR and MeR regions by southerly flows (wetness SPEI conditions in fall) and cause to appear below‐normal PM10 values in the southern stations.

This study aimed to analyse the spatio‐temporal variability of wet and drought events in the Paraná River Basin and their association with the El Niño—Southern 20 Oscillation (ENSO) phenomenon. A dataset of daily precipitation from 953 pluviometric stations from 1982 to 2016 was used. Anomalies of sea surface temperature (SST) from the four Niño regions of the Equatorial Pacific were also used. Homogeneous rainfall regions were defined using cluster analysis and principal component analysis (PCA). To describe the drought or wet conditions the standardized precipitation index (SPI) for 1‐, 3‐, and 12‐months time scales were used. The relationship between the ENSO and the wet and drought conditions were also analysed. The results suggest that two regions are enough to represent the whole Paraná River Basin during different rainfall patterns. In the 1‐month SPI, the precipitation extremes of the region that is mainly composed of the state of Paraná and southern region of Mato Grosso do Sul (Region 2), showed a statistically significant correlation at the level of 1% with ENSO events. In the 12‐month SPI, the most intense drought and wet events and with greater spatial coverage, in general, were observed in years with ENSO occurrences. In general, it is observed that although the ENSO phenomenon is not the main factor that causes the drought and wet events in the region, El Niño contributes to the rainfall excess and La Niña to the rainfall deficit in the Paraná River Basin.

<p indent="0mm">Precise mapping of surface water is of great importance for water resource management, ecological environment protection, and flood disaster mitigation. However, the Songliao Basin still lacks a high-precision, long-term surface water distribution dataset. To address this gap, this paper, based on satellite remote sensing data (Landsat-5/7/8/9) and implemented on the Google Earth Engine (GEE) platform, developed a surface water extraction algorithm suitable for the Songliao River Basin. It produced an annual surface water distribution dataset from 1984 to 2023. This dataset includes an annual Water Body Frequency (WBF) dataset and a Surface Water Classification (SWC) dataset, covering seasonal water bodies, permanent water bodies, and annual maximum water extent. Through accuracy assessment, the overall accuracy of the water extraction method reached 98%, with a Kappa coefficient of 0.95. To verify the reliability of the dataset, the SWC dataset was compared with the Global Surface Water (GWS) historical dataset. The results show that the SWC dataset achieves higher classification accuracy than the GWS dataset in multiple subregions of the Songliao Basin. The high-precision water dataset provided by this research offers important support for the monitoring and sustainable management of water resources in the Songliao Basin and lays a solid data foundation for scientific research in related fields.

Investigating the changes in groundwater aquifers in planning the sustainable management of water resources in each region is of particular importance. Therefore, reducing the level of groundwater aquifer changes requires proper management and planning to exploit water resources. In this study, the level of groundwater aquifer changes in Urmia Lake basin was examined for the period from 2002 to 2017 using GRACE satellite data (JPL, GFZ, CSR triple bands, CRI Filtered model, time and space filter, and Lew-Thiknth uncertainty dry product) in the Google Earth Engine. The results of the triple bands showed that the JPL band estimated the average level of groundwater aquifer changes on May 1, 2004 as 14.947 cm, while the GFZ band on estimated this as -30.558 cm on September 1, 2015 and the CSR band estimated this amount as -28.206 cm. Therefore, CRI Filtered model can very accurately identify the boundary between land and water zones. The results showed that this model estimated the maximum thickness of liquid water in the groundwater aquifer at March 31, 2002 as about 11.599 cm and its uncertainty at about 9.767 cm. It can be said that the least amount of thickness of liquid water is estimated on 13 August 2015 as 12.309 cm with an uncertainty level of 10.759 cm. According to the results, the level of groundwater change in aquifers in terms of liquid water thickness parameter (Lew-Thiknth) in the northern parts of the Urmia Lake basin and in terms of uncertainty in the northeastern part of the Urmia Lake basin is experiencing a strong decline in the aquifer water levels.

&amp;lt;p&amp;gt;Global climate change models predict an increase in both the frequency and severity of extreme weather events, including prolonged drought conditions, thus posing a unique set of challenges for regions traditionally unaccustomed to severe climate phenomena. This is particularly significant for the occurrence of severe drought events in areas characterised by temperate maritime climates, such as the Republic of Ireland (ROI). While numerous studies have explored the impacts of drought on groundwater levels and chemical contamination, few studies have sought to investigate the impacts of sporadic drought events on the microbial quality of groundwater for human consumption. Accordingly, the 2018 (June-August) European drought event represented a unique opportunity to investigate the effects of prolonged low rainfall and elevated temperature (relative to seasonal means) on the incidence of faecal indicator organisms (FIOs) among unregulated domestic groundwater supplies in the ROI.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;A dual-sampling fieldwork regime (during and post-event) of private wells (n=74) and subsequent risk factor (logistic regression) and bivariate analyses were used to evaluate the potential role of meteorological and site specific (hydrogeology, contaminant sources etc.) conditions on the incidence of microbial contamination. During absolute drought conditions (&amp;amp;#8805;15 days characterised by no measureable precipitation, June 2018), the sampled cohort exhibited a significantly decreased risk of microbial contamination (OR: 0.356, p = 0.024) with 12.2% (n = 9/74) of supplies contaminated with Escherichia coli (E. coli), increasing to 28.4% (n = 21/74) upon abatement of drought conditions (October 2018). No analysed risk factors were associated with E. coli presence at the 95% confidence level, although, the presence of onsite domestic wastewater treatment systems (U = 1.03 p = 0.057) approached statistical significance during the drought. Findings suggest that the 2018 European drought served to decrease background levels of FIO within private wells in the ROI, likely due to reduced hydraulic loading from the surface, soil moisture deficits and consequently, significantly decreased bacterial survival. Results would seem to reiterate the significance of onsite domestic wastewater treatment systems as a source of subsurface contaminants in Ireland. The presented opportunistic field study provides a critical characterization of the impacts of unprecedented drought events on microbiological water quality in domestic groundwater supplies in temperate regions, and may be used by sanitary/environmental engineers, hydrologists, hydrogeologists, policy-makers, planners and healthcare practitioners to safeguard against the future human health effects of climate change and extreme weather events. &amp;amp;#160;&amp;amp;#160;&amp;lt;/p&amp;gt;

The Darfur conflict, which emerged in the early 21st century, represents a multifaceted crisis driven by socio-political and environmental factors, with resource scarcity, exacerbated by climate change, playing a pivotal role in intensifying tensions between agricultural and pastoral communities. While climate change is typically associated with adverse environmental outcomes, an analysis of data spanning four decades (1980–2023) reveals a contrasting trend of increased precipitation, enhanced vegetation, and decreased drought frequency in recent years. This research explores the potential of these positive environmental changes to mitigate resource-based conflicts and foster political stability in Darfur as improved environmental conditions are posited to create a foundation for conflict resolution and sustainable peacebuilding. The present study integrates trends in the Enhanced Vegetation Index (EVI) and the Standardized Precipitation Evapotranspiration Index (SPEI) to examine these shifts. EVI data, derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) at a 250 m resolution, was used to assess large-scale vegetation patterns in arid and semi-arid landscapes. The Autoregressive Integrated Moving Average (ARIMA) model was employed to forecast future precipitation scenarios up to the year 2034, enhancing the understanding of long-term climatic trends. Data processing and analysis utilized advanced tools, including Google Earth Engine (GEE), ArcGIS Pro (version 3.4), and R software (version 4.3.2). The findings reveal a significant (33.19%) improvement in natural vegetation cover between 2000 and 2023, with degraded and unchanged areas accounting for 1.95% and 64.86%, respectively. This finding aligns with a marked increase in annual precipitation and a reduction in drought intensity over the study period. Historical SPEI analysis showed persistent drought events between 1980 and 2012, followed by a notable decline in drought frequency and severity from 2013 to 2024. Precipitation projections suggest a stable trend, potentially supporting further vegetation recovery in the region. These environmental improvements are preliminarily linked to climate-change-induced increases in precipitation and reductions in drought severity. This study’s findings contribute to a nuanced understanding of the interplay between environmental dynamics and socio-political stability in Darfur, offering actionable insights for policy interventions aimed at fostering sustainable peace and resilience in the region.

The Mediterranean area is one of the most important “hotspot” where the effects of climate change are more evident, with an increase of extreme events such as hot waves and intense droughts. From this perspective, central Italy, which in the recent past suffered from the impact of intense negative anomalies of precipitation on water resources, shows peculiar characteristics, being its meteoclimatic regime determined by global, regional and local factors. In this context, this study aims at exploring the variability in time and space of the precipitation regime in central Italy over the period 1960–2020 analysing global factors, represented by indexes of teleconnection, and local factors such as orography and distance to the sea. Findings indicate an increase of drought events during the last 20 years, in a general pattern characterized by stationary precipitation amounts. This trend is clearer on the Tyrrhenian coast with a number of months under severe drought conditions increasing from 5% (1965–1999) to 24% (2000–2020). The strengthening of the periodic signal of precipitation is related mainly to the Atlantic Multidecadal Oscillation Index and the Western Mediterranean Oscillation Index. Considering the relationship between precipitation and teleconnection patterns over short time scales (few months), correlations are stronger with the North Atlantic Oscillation index and in general with the Atlantic patterns rather than with the Artic patterns, especially for the Adriatic side.

Drought is a recurrent hazard with significant ecological and socioeconomic impacts, requiring continuous monitoring and assessment. This study evaluates the occurrence and spatial-temporal distribution of drought in the Megech-Dirma Watershed, Ethiopia, over the period 2001-2022. Agricultural drought indices Vegetation Condition Index (VCI), Temperature Condition Index (TCI), Vegetation Health Index (VHI) and the meteorological Standardized Precipitation Index (SPI) at 3-month temporal scales were analyzed using the Google Earth Engine platform. The time-series analysis revealed minimum VCI values, indicating severe drought, in 2009 and 2010, while moderate to no drought conditions dominated during 2001 to 2009 and 2010 to 2021. Moderate droughts also showed a declining trend in 2009 and 2010. The TCI series identified frequent extreme drought events in 2002, 2003, 2004, 2009, 2013, 2016, and 2019, with severe drought recorded in 2006, 2007, 2010, 2014, 2015, 2017, 2021, and 2022. Mild to moderate droughts occurred in 2001, 2002, 2008, 2018, 2020, and 2022. Minimum VHI values, also indicating severe drought, were observed in 2002, 2003, 2004, 2009, 2012, 2013, and 2016, while 2001, 2006, 2007, 2010, 2014, 2015, and 2017 to 2022 were dominated by mild to moderate drought conditions. SPI revealed moderate drought conditions, showing weak correlations with the vegetation-based indices (correlation coefficients: -0.08 with TCI, -0.04 with VCI, and - 0.06 with VHI). Drought severity increased spatially in the watershed's northern regions. Of the total area, 9.63% experienced extreme drought, 20.95% severe drought, 29.12% moderate drought, 26.94% mild drought, and 13.36% no drought. Drought hazard maps revealed extreme and severe drought concentrated in the northern and southern parts, whereas moderate, mild, and no drought conditions were distributed across the southwest, east, and central regions. These findings highlight the spatial-temporal complexity of drought in the watershed and provide a robust basis for drought monitoring, water resource management, and ecological protection. The results emphasize the importance of continuous observation, proactive measures, and adaptive strategies to mitigate the impacts of drought.

The sustainable management of water resources remains critical to environmental protection, public health, and ecological stability within the European Union (EU).This study evaluates recent EU progress regarding wastewater treatment infrastructure, analyses water quality indicators including organic pollutants, nitrates, and phosphates, and examines climate-induced pressures, particularly drought events, affecting freshwater availability.Our assessment is based on statistical analyses from Eurostat and the European Environment Agency (EEA).Results demonstrate improvements in wastewater treatment connectivity, with EU average connections to secondary treatment systems rising significantly from 72.6 % in 2006 to 80.9 % in 2021.However, despite advances, water quality challenges persist, notably eutrophication driven by stable nitrate levels in groundwater (averaging 20.5 mg/l in 2021) and increasing phosphate concentrations in rivers (up by 21.3 % since 2016).Concurrently, climatic impacts, especially drought events, have exacerbated water stress, significantly affecting about 29 % of the EU territory periodically.Comparative data from Serbia reveals similar challenges but underscores significant gaps in wastewater treatment coverage and water quality, highlighting the importance of strategic regional and EU-wide water governance measures.Effective policy implementation and investment in sustainable water infrastructure are essential to counteract environmental degradation and ensure long-term freshwater security.

As climate change drives the intensification and increased frequency of hydrological extremes, the need to balance drought resilience and flood protection becomes critical for proper water resources management. Extreme droughts in the last decade in Germany have caused significant damages to ecosystems and human society, prompting renewed interest in sustainable water resources management. At the same time, protection from floods, such as the catastrophic flood in the Ahr Valley in 2021, weighs heavily on the public conscience. In the state of Baden-Württemberg in southwestern Germany alone, over 600 small (&lt; 1 million m$^3$) to medium-sized (1–10 million m$^3$) reservoirs are currently operated for flood protection. In this study, we investigate the potential of different reservoirs to implement a dual flood–drought protection scheme that introduces a retention flow to store excess water for release in drought conditions, assuming that locations with more water available for storage will be better able to mitigate downstream streamflow drought. In total, 30 reservoirs in Baden-Württemberg were selected based on their size according to the German design standard DIN19700 (where small reservoirs have capacities of roughly 50 000–100 000 m$^3$, medium have capacities of 100 000–1 000 000 m$^3$, and large have capacities of more than 1 000 000 m$^3$), their purpose (flood-only or multipurpose), and their relative water availability (expressed as the number of times the reservoir can be filled by the difference between the mean inflow and mean low flow). These reservoirs, despite their DIN19700 sizing categories, are small in the context of global reservoir studies. Daily target releases for drought protection are proposed based on the 70th percentile exceedance of modeled inflows from the calibrated LARSIM hydrological model. The retention flow is optimized to maximize penalty reduction in a scenario of perfect knowledge of flooding by using meteorological observations as artificial weather forecasts in LARSIM. The re- sults of different retention flows are then evaluated based on their adherence to target releases and flood protection performance. Reservoirs were required to maintain the same level of flood protection under these modified rules. The optimized results were varied: some reservoirs can release up to 80 times their capacity with limited benefit for streamflow drought prevention; others can reduce streamflow drought conditions and water deficits by almost 95 % over a 24-year simulation period; and others have potential but are limited by either their capacity or flood protection constraints. There seems to be a trade-off between the relative water availability at the reservoir and the ability to alleviate drought conditions. We find that relative water availability at the reservoir has a strong relation to the amount of water a reservoir can release for drought protection, but it fails to summarily describe the reservoir’s potential impact on drought conditions downstream.

Drought directly and indirectly affects human society in a number of ways. In many regions of the world climate change will exasperate the effects of droughts, affect national economies more intensely. The main aim of this article was to catalogue and analyze the drought impacts in the 11 Central and South Eastern European states located in the Danube river basin. The identification of dry episodes was based on information from publicly available sources, namely, newspaper and journal articles that reported drought impacts. Information on drought impact occurrences was classified into one of five defined categories in which the drought impact report was most clearly manifested (i.e., agriculture, forestry, soil systems, wildfires and hydrology). In terms of the spatial distribution of drought impacts, individual recorded events were analyzed at the level of EU NUTS regions (or their equivalent in non‑EU countries). The analysis highlights country‑specific vulnerability to drought. Furthermore, gradual increases in drought events and the number of reported impacts were identified, which was particularly evident in the agricultural sector.

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Climate change is causing an increase in drought events around the world. Water limitation affects the quality and quantity of plant resources for herbivorous insects, resulting in cascading effects for higher trophic levels. Physiological changes due to water limitation may make plants more nutritious for insect herbivores, but it comes at the cost of increased plant defensive responses, declining biomass, and restricted access to the phloem. These changes in the plant have direct effects on natural enemies of herbivorous insects by changing the attractiveness of the habitat, and indirect effects by changing the quality of their insect prey. However, the outcomes of these interactions are still up for debate. My research examined the broad effects of water limitation on insect communities and elucidated mechanisms driving the response. This research is novel in that I assessed insect responses to multiple levels of water limitation and across several levels of ecological organization: plant-herbivore, tri-trophic, and within the framework of the greater arthropod community. First, I examined effects of plant water limitation on the arthropod community associated with wheat (Triticum aestivum L.), with specific focus on aphids and their natural enemies. Second, I determined how plant water limitation affects bird cherry-oat aphid (Rhopalosiphum padi) performance and population growth, and investigated plant traits that influence the aphid response. Third, I assessed aphid behavioral responses to plant water limitation and their contribution to aphid performance outcomes. Finally, I determined the indirect consequences of plant water limitation for aphid population suppression by parasitic wasps. Across all studies, I found evidence that aphid populations may decline as droughts become more frequent and intense. I determined that all levels of water limitation reduced total insect abundance and shifted the composition of the insect community. Using structural equation modeling, I showed that aphids were affected by stress induced changes in plant properties other than plant biomass, whereas natural enemies were strongly affected by changes in plant biomass; these effects were exacerbated as water stress increased. Aphid population size, population growth rate, and individual fecundity were negatively affected by even mild levels of plant water limitation. Diminished aphid performance on stressed plants may be driven by reduced amino acid concentrations and increased sucrose concentrations, both conditions which reduce plant quality for aphids. In addition, aphid host-plant selection was affected by plant water limitation, and aphid feeding rate declined on stressed hosts. Finally, parasitic wasps were better at suppressing aphid populations on stressed plants, with the highest mummy production found under mild stress conditions. However, the mechanism driving improved aphid suppression by wasps on stressed plants was reliant on water stress intensity. Taken together, I found that plant water limitation negatively affects insect communities and influences tri-trophic interactions. These studies highlight the intricate ways plant water stress intensity can affect insect behavior, performance, and species interactions, which are critical for our ability to predict outcomes of a changing climate for insects.

Urban areas often have low soil water availability due to their impervious surfaces reducing rainfall infiltration. These water-limited conditions may be exacerbated by the projected increases in drought events caused by climate change. As a result, plants that grow in urban areas are vulnerable to drought stress. There are a range of practices that can be used to help mitigate drought stress, including the use of biostimulants. This study aimed to determine whether biostimulant application (1) improves plant performance and (2) mitigates the drought stress on urban plant species. To address these aims, we selected six woody and three graminoid plant species that are commonly planted in Australian urban areas and exposed them to different watering (drought-stressed, well-watered) and biostimulant (control, humic acid, protein hydrolysate, seaweed extract) treatments. We then measured their assimilation rate, growth metrics and biomass allocation. We found that drought stress reduced the assimilation rates and shoot growth of the study species. However, this did not translate into a biomass reduction because the drought-stressed plants reallocated resources towards root biomass. We found no evidence to suggest biostimulant application mitigated the impacts of drought stress on plant performance. Further, the only effect biostimulant application had on plant performance irrespective of the watering treatment was that the seaweed biostimulant increased the plant height growth of the woody species. These results show that the biostimulants used in this study will have a limited effect on the performance of plant species commonly planted in Australian urban areas.

What if the rains do not come?