High Evapotranspiration Rates Research Articles

Larger shrubs can maintain high infiltration and evapotranspiration rates in experimental biofiltration systems impacted by high sediment loads

Biofiltration systems can fail over time due to clogging by fine sediments in stormwater. Infiltration can be maintained by plant roots, but species selection for biofiltration to date has largely been driven by pollutant removal efficiency and tolerance of conditions. As a result, plant species diversity in biofilters is typically low and dominated by sedges and rushes. Increased use of woody species could in theory improve plant diversity, aesthetic appeal, infiltration under high sediment loads and volumetric runoff reduction via higher evapotranspiration, without jeopardising nutrient pollutant removal. We tested whether shrubs could maintain infiltration and evapotranspiration in biofiltration profiles treated with a high sediment load, by comparing them with biofilters subjected to tap water without sediment. Following sediment application, biofilter columns planted with shrubs with high total biomass and total root length showed higher infiltration and evapotranspiration than those receiving tap water. These results indicate that shrub species are likely to alleviate clogging and increase stormwater retention in biofiltration systems. However, shrubs with a high root diameter also had low total biomass and total root length and showed 33–51 % lower infiltration rates after sediment application compared with those receiving tap water. As all shrubs had higher root diameters than typical sedges and rushes, we suggest that shrubs need a combination of higher total biomass, total root length and average root diameter to effectively maintain infiltration. While shrubs which maintained infiltration had traits associated with high nutrient removal, nutrient removal efficiency of shrubs needs to be quantified. Although root traits were related to maintenance of infiltration, above-ground stems likely created flow pathways through sediment which requires further investigation. Overall, selecting shrub species with high total biomass has the potential to maintain infiltration and increase evapotranspiration in biofiltration systems impacted by high sediment loads.

Direct observations of evapotranspiration from three contrasting vegetation types on a coastal low-lying sub-tropical sand island

Coastal low-lying sand islands confront an imminent threat owing to global warming, primarily stemming from the confluence of rising sea levels and amplified precipitation variability. These islands harbour delicate freshwater reservoirs in unconfined aquifers, reliant significantly upon precipitation for replenishment. This investigation focuses on a sand island situated along Australia’s eastern coast, resembling islands prevalent across the Indian and Pacific Oceans. The study involves comprehensive instrumentation to monitor Actual Evapotranspiration (AET) concurrently with rainfall patterns and water table fluctuations. Eddy Covariance (EC) systems were employed across three distinct vegetation zones: a wetland, a swamp, and a commercially managed pine forest plantation. The aim was to gauge evapotranspiration dynamics, comparing computed reference evapotranspiration (ET0) at each site with EC-measured values to establish novel reference vegetation coefficients (Kv) tailored to these specific environments. Actual evapotranspiration was found the largest at the wetland, the swamp, and the pine plantation in decreasing order. Pine plantation evapotranspiration was found the most sensitive to water table depth, while the native swamp and wetland maintained high evapotranspiration rates through dry periods. A simple idealized water balance is proposed for the island for the dry and wet seasons. Large rainfall events during the wet season were found critical in providing recharge of the aquifer, highlighting the importance of such events in maintaining the freshwater resource and vegetation health on such islands.

Understanding the drivers of the catchment hydrological cycle of the Jonkershoek Valley catchment, South Africa

Understanding trends in hydro-climate variables and the impacts of land use on the streamflow is crucial for the development of appropriate catchment water management strategies. Jonkershoek (146 km2) is an important headwater catchment in the Table Mountain Group (TMG) geological region, contributing flow to the Cape Winelands District Municipality in the Western Cape. This study analyses hydro-climate variables at annual, monthly, and seasonal scales using an integrated approach composed of statistical homogeneity testing for abrupt changes, Mann-Kendall tests for trend analysis, and the Indicators of Hydrological Alteration (IHA) tool for streamflow alterations. Analyses were conducted for three headwater sub-catchments within the Jonkershoek value, each with different land use history.Homogeneity test of rainfall and streamflow data spanning from 1946 to 2019 identified gradual downwards change points for annual rainfall and streamflow across the sub-catchments. Moreover, the change points for streamflow were inconsistent with those of rainfall. The identified change points in streamflow were consistent with the timing of afforestation activities in Tierkloof, whereas in Bosboukloof and Langrivier they could be attributed to earlier climatic variability. Furthermore, Mann-Kendall test detected significant (p < 0.05) decreasing trends for both annual and seasonal rainfall which coincided with most of the streamflow trends. Trends were strongest for the winter season suggesting a possible shift in climate patterns which influence winter rainfall. Winter streamflows declined by 15.5%–39.5%. Analysis of hydrological flow indices indicated significant decrease in 1-,7- and 30-day annual maximum extremes during afforestation which were attributed to high evapotranspiration rates of pines. The opposite was observed during clearfelling period in Bosboukloof. The median monthly flow also showed a decrease for winter months. This shows that climate variability and land-use change by afforestation have major impacts on streamflow. The findings of this study are important to inform policymakers on the impacts of climate change and land use, allowing pro-active mitigation and adaptation.

Selection of tropical plants for an extensive green roof with abilities of thermal performance, energy conservation, and greenhouse gas mitigation

The development of green roofs to mitigate urban heat island effect is critical for conserving energy and reducing carbon footprint. This study evaluated the thermal performance of an extensive green roof design compared with a conventional roof and assessed the suitability of thirty-two plants for low-maintenance green roofs in a tropical area. Experiments were carried out in four phases, covering the tropical climatic conditions from June 2016 to December 2017. The results indicate that a green roof temperature was significantly lower than that of a conventional roof by 12 °C. This led to an 84 % reduction in heat transfer through the building, potentially leading to a decrease in electricity consumption by 0.20 kWh/m2/8 h and saving electricity costs by 0.019 USD/m2/8 h, achieved through a reduction in the cooling load on air conditioners. The highest carbon dioxide removal achieved in this study was 3.01 kgCO2/m2, with an effective mitigation of greenhouse gases by 28.46 kgCO2eq/m2/year. The top three plant species recommended for a low-maintenance green roof are Dracaena cochinchinensis, Santisukia kerrii, and Dracaena kaweesakii. The plant characteristics for low-maintenance green roofs in tropical climates include drought and extreme weather tolerance, disease and insect resistance, short and spreading roots, succulent leaves with ability to store water, low water requirements, slow growth rate, easy availability locally and affordability, thriving in low-nutrient conditions, and a high evapotranspiration rate. In applicable contexts, green roofs designed with suitable tropical plants could potentially enhance urban environments and contribute to achieving low-carbon and environmental sustainability.

Analysis of Spatial and Temporal Variations in Evapotranspiration and Its Driving Factors Based on Multi-Source Remote Sensing Data: A Case Study of the Heihe River Basin

The validation of remotely sensed evapotranspiration (ET) products is important for the development of ET estimation models and the accuracy of the scientific application of the products. In this study, different ET products such as HiTLL, MOD16A2, ETMonitor, and SoGAE were compared using multi-source remote sensing data and ground-based data to evaluate their applicability in the Heihe River Basin (HRB) during 2010–2019. The results of the comparison with the site observations show that ETMonitor provides a more stable and reliable estimation of ET than the other three products. The ET exhibited significant variations over the decade, characterized by a general increase in rates across the HRB. These changes were markedly influenced by variations in land use and topographical features. Specifically, the analysis showed that farmland and forested areas had higher ET rates due to greater vegetation cover and moisture availability, while grasslands and water bodies demonstrated lower ET rates, reflecting their respective land cover characteristics. This study further explored the influence of various factors on ET, including land use changes, NDVI, temperature, and precipitation. It was found that changes in land use, such as increases in agricultural areas or reforestation efforts, directly influenced ET rates. Moreover, meteorological conditions such as temperature and precipitation patterns also played crucial roles, with warmer temperatures and higher precipitation correlating with increased ET. This study highlights the significant impact of land use and climatic factors on spatiotemporal variations in ET within the HRB, underscoring its importance for optimizing water resource management and land use planning in arid regions.

Post-landslide restoration through multistrata agroforestry-based land management in the West Bogor area of Indonesia

The West Bogor area experienced a landslide disaster, causing extensive damage to secondary forest areas, plantations, and residential homes. Despite evacuations, the community persists in using the affected land for agriculture. This study aims to develop a land management model based on agroforestry for post-landslide restoration, to prevent landslide reactivation, and to provide benefits for the local community. Introducing an agroforestry system that includes deep-rooted trees and perennial crops on landslide-prone slopes can improve slope stability by enhancing soil structure and water retention, minimising erosion and landslides. The study examines unexplored aspects of landslide characteristics and zoning as a novel approach to improve mitigation strategies. We classify the post-landslides area into depletion, transition, and accumulation zones. The lithology comprises Breccia with pumice and Andesite gravels, a sandy tuff matrix, and Claystone underneath, acting as the slip surface. The northern landslide has depletion, transition, and accumulation zones ranging from 743 to 710 m above sea level (masl), 710 to 694 masl, and 694 to 676 masl. In the southern landslide, these zones range from 783 to 720 masl, 720 to 705 masl, and 705 to 676 masl. Based on the characteristics of those zones, we develop an agroforestry model in a vertical pattern with species strata, fast-growing local plants, strong and deep roots, and a relatively high evapotranspiration rate. The depletion zone is managed as a complex agroforestry system (forest type) consisting primarily of forest plants and plantation crops. The transition zone is a complex agroforestry (garden type) with plantation crops and some forest plants. The accumulation zone is a simple agroforestry system with seasonal crops. On almost flat land in an accumulation zone suitable for Oryza sativa cultivation, we apply Cocos nucifera as a protective plant. Soil fertility in all zones is improved with organic and inorganic fertilization, and it also increases the mycorrhizal population through the planting of leguminous plants. The multistrata agroforestry model, created and adapted to the specific characteristics and zoning of landslide-prone areas, is expected to significantly enhance landslide restoration and erosion mitigation and reduce the risk of future landslides. Such approaches can be extended to regions with comparable characteristics.

Quantifying the Distribution of Evapotranspiration at PV and APV Sites Using Soil Moisture

Solar panels affect the distribution of water and energy reaching the ground causing changes in soil moisture, evapotranspiration and percolation. In the context of Agri-Photovoltaics those changes influence plant growth and yield as well as irrigation demands while large Photovoltaic installations could potentially lead to changes in the water balance of the catchment. In either case, evapotranspiration plays an important role as the installation of panels of any design leads to shading thereby reducing the water loss to the soil through evapotranspiration. As it is difficult to measure evapotranspiration, the authors proceeded using soil moisture observations to quantify evapotranspiration pattern in dry periods. They found on average a 44 % higher evapotranspiration rate over 12 dry periods of varying conditions under the panels compared to a reference area at the research site Pillnitz. However, similar observations at the second site, Weesow show also a reversed behaviour due to reduced soil water availability as a result of the higher evapotranspiration at the reference area.

High-resolution mapping and multivariate technique (factor analysis) to support hydrogeochemical analysis and identification of surface water contamination

The study presented a high-resolution regional mapping of a significant Brazilian watershed, which is heavily influenced by mining, agriculture, and domestic/industrial effluents. Upper São Francisco Basin encompasses the largest karst area in the country and includes three important Brazilian biomes: Cerrado, Atlantic Forest, and Caatinga. Surface water (1418 samples) was collected during the dry season and was analyzed for physical-chemical parameters, cations, anions, and some metals. The spatial distribution and abundance of variables were assessed, and the processes controlling the sources of dissolved loads in surface waters were discussed. The results indicate that rock weathering is the primary factor controlling water chemistry, with a strong influence of carbonate and silicate minerals. Anthropogenic activities, particularly agriculture, play a key role in the chemical composition of the microbasins. Soil erosion and leaching processes also contribute significantly to the region, driven by land use practices and mineral extraction, which intensify erosion processes. The northern sector of the Upper São Francisco Basin, characterized by an arid climate and Caatinga vegetation, experiences low precipitation and high evapotranspiration rates. The VG stands out due to the presence of the karst zone and for the mixture of natural to anthropogenic sources.

Increased panicle nitrogen application improves rice yield by alleviating high-temperature damage during panicle initiation to anther development.

The grain yield is closely associated with spikelet fertility in rice (Oryza sativa L.) under high temperatures, and nitrogen (N) plays a crucial role in yield formation. To investigate the effect of panicle N application on yield formation under high temperatures at the panicle initiation stage, two rice varieties [Liangyoupeijiu (LYPJ, heat susceptible) and Shanyou63 (SY63, heat tolerant)] were grown and exposed to high daytime temperature (HT) and control temperature (Control) during the panicle initiation stage. Low (LPN) and high (HPN) panicle N applications were conducted. HT markedly decreased the yields by 87% at LPN and 48% at HPN in LYPJ and 31% at LPN and 36% at HPN in SY63. The decrease in grain yield under HT was primarily attributed to the decline in spikelet fertility, HPN increased spikelet fertility. HT resulted in the abnormal development of anthers, which included disordered, enlarged, and broken anther wall layers, degraded and irregularly shaped microspores, delayed tapetum degradation, less vacuolated microspores per locule, abnormal and aborted pollen grains; however, HPN improved the development of anthers under HT, particularly in LYPJ. A high rate of evapotranspiration resulted in an approximately 1°C decrease in panicle temperatures at HPN compared with that at LPN in both varieties under HT. Overall, these results demonstrate that the increased panicle N application favors normal anther development in LYPJ by decreasing the panicle temperature, which results in high pollen viability and spikelet fertility, and consequently less yield loss under HT.

Seasonal soil moisture thresholds inhibit bacterial activity and decomposition during drought in a tallgrass prairie

Soil moisture reductions during drought often inhibit soil microbial activity and inhibit decomposition rates by reducing microbial biomass or by altering microbial communities. Evidence suggests that soil water must drop below a critical threshold to inhibit microbial activity. Thus, it is likely that the seasonal timing of drought will determine the extent to which belowground processes are adversely impacted by drought. Specifically, the effects of drought might be minimal during cool, wet periods typical of late spring but dramatic during hot summer months with high evapotranspiration rates that lower soil moisture levels below the critical threshold. Here, we present results from a study designed to quantify the effect of drought on soil microbial abundance, community composition, and soil water diffusion across four months, and to then assess how drought impacts the microbial decomposition of leaf matter. We imposed a season‐long drought in a Wisconsin tallgrass prairie and measured soil moisture, bacterial composition and abundance, microbial respiration, and decomposition rates throughout the growing season. Bacterial communities varied considerably among dates, but drought did not affect either bacterial abundance or community composition. Microbial respiration declined significantly during periods of drought when soil pores likely became hydrologically isolated, ultimately reducing cumulative microbial respiration by 10%. The reduction in microbial activity in drought treatments caused a 50% decline in the decomposition of refractory material. Our study highlights that sublethal effects of drought on microbial communities, occurring only when soil moisture declined below a tolerance threshold, can have large impacts on microbial carbon release or decomposition, highlighting the need to incorporate such measures into future studies.

Hydrogeochemical study of groundwater in arid and semi-arid regions of the Infracenomanian aquifers (Cretaceous Errachidia basin, Southeastern Morocco). Using hydrochemical modeling and multivariate statistical analysis

Groundwater in the Cretaceous Errachidia basin, located in the southern part of Morocco, is crucial in supporting the region's main economic activities, such as farming. This arid region faces multiple challenges, including an average annual rainfall of less than 80 mm/year, intense agricultural activities, high evaporation, and extremely high evapotranspiration rates up to 1580 mm/year. Therefore, the hydrogeochemical study focuses on the Infracenomanian aquifers in the Cretaceous Errachidia basin. The goal is to evaluate the sustainable use of saline lands and brackish water, particularly assessing water resources and sustainable socioeconomic development in southeastern Morocco. In June 2021, 20 samples were collected and analyzed for pH, electrical conductivity (EC), total dissolved solids (TDS) and major ions. The hydrogeochemical parameters were analyzed using multivariate statistical methods. Statistical techniques such as Piper's trilinear diagram analysis of hydrochemistry types, Gibbs diagram analysis, The HFE diagram and ion correlation analysis were used to examine the origins of the main ions in the groundwater and to determine the source of the salinization processes in the groundwater.The findings revealed a strong positive correlation between TDS and the spatial distribution of major ions (Na+, Ca2+, Mg2+, Cl−) and EC, revealing high mineralization in the study area. The main cations in groundwater are Na+ and Ca2+, while the main anions are Cl−. The elevated concentrations of Cl− and Na+ are due to the evapotranspiration of irrigation water. Furthermore, the hydrochemical facies types are predominantly sodium chloride (Na–Cl), followed by calcium chloride (Ca–Cl) and a mix of calcium and magnesium chloride facies (Ca–Mg–Cl). These analyses indicate that the hydrochemistry of groundwater in the study area is primarily influenced by water-rock interactions, such as the dissolution of sedimentary rocks, soil leaching through gravity irrigation, and evaporation in the region. Moreover, the analysis using the Gibbs diagram indicates that evaporation is the primary hydrogeochemical process that shapes the chemical composition of the groundwater in the area under study.

Simulation of Irrigation Strategy Based on Stochastic Rainfall and Evapotranspiration

The North China Plain plays a pivotal role in China’s crop production, contributing to 30% of the maize yield. Nevertheless, summer maize in this region faces challenges due to climatic constraints characterized by concurrent high temperatures and rainfall during the growing season, resulting in a relatively high evapotranspiration rate. In this study, we explored eight soil moisture-based threshold irrigation strategies, consisting of two upper limits and four lower limits, along with a rainfed mode (E). The upper and lower irrigation limits are expressed as a percentage of the field’s water-holding capacity (sfc). For the four full irrigation modes (A1, A2, A3, A4), the lower limits were set at 0.6 sfc, 0.6 sfc, 0.5 sfc, and 0.5 sfc, respectively. The upper limits were defined at two levels: 0.8 sfc for A1 and A2 and sfc for A3 and A4. Similarly, for the four deficit irrigation modes (B1, B2, B3, B4), the lower limits were established at 0.4 sfc, 0.4 sfc, 0.3 sfc, and 0.3 sfc, respectively, with the upper limits set at two levels: 0.8 sfc for B1 and B2 and the full sfc for B3 and B4. To investigate the impact of rainfall and potential evapotranspiration on these irrigation modes under long-term fluctuations, we employed a stochastic framework that probabilistically linked rainfall events and irrigation applications. The Monte Carlo method was employed to simulate a long-term series (4000a) of rainfall parameters and evapotranspiration using 62 years of meteorological data from the Xinxiang region, situated in the southern part of the North China Plain. Results showed that the relative yield and net irrigation water requirement of summer maize decreased with decreasing irrigation lower limits. Additionally, the interannual variation of rainfall parameters and evapotranspiration during the growing season were remarkable, which led to the lowest relative yield of the rainfed mode (E) aligned with a larger interannual difference. According to the simulation results, mode A4 (irrigation lower limit equals 0.5 sfc, irrigation upper limit equals 0.8 sfc) could be adopted for adequate water resources. Conversely, mode B2 is more suitable for a lack of water resources.

Impact of Soil Surface Temperature on Changes in the Groundwater Level

The relationship between the soil surface temperature and groundwater level is complex and influenced by various factors. As the soil surface temperature increases, water evaporates quickly from the soil, which can lead to a decrease in the groundwater level. In this study, we analyzed the impact of soil surface temperature on changes in the groundwater level in the Bukhara region of Uzbekistan using data from 1991 to 2020. The Bukhara region experiences regular water shortages, increased soil salinization, and inefficient energy in lift-irrigated areas, which is a typical constellation of challenges to the water–energy–food–environment (WEFE) nexus. The soil surface temperature data were collected from the Hydrometeorological Service Agency, whereas groundwater level data were obtained from the database of the Amelioration Expedition under the Amu-Bukhara Basin Irrigation Systems Authority. We used linear regression analysis and Analysis of Variance (ANOVA) tests to establish the significance of the relationship between the soil surface temperature and groundwater level, as well as the impact of the location of the groundwater level measurements. The results indicate that the model was a good fit to the data, and both the intercept and the soil surface temperature were significant factors that affected groundwater level. The results further suggest that the strength of the relationship between solar radiation and soil surface temperature is very high, with a correlation coefficient of 0.840. This means that when solar radiation increases, soil surface temperature also tends to increase. The analysis also showed that 53.5% of the changes in groundwater level were observed by the regression model, indicating a moderately correlated relationship between the groundwater level and soil surface temperature. Finally, higher solar radiation leads to higher soil surface temperature and higher evapotranspiration rates, which can lead to a decrease in groundwater level. As a result, we observe that the soil surface temperature determines changes in the groundwater level in the study region.

Developing a sustainable water conservation strategy for Saudi Arabian cities

Water scarcity is a global issue posing significant challenges for sustainable water management. Saudi Arabia, due to its arid conditions, limited freshwater resources, and high evapotranspiration rates, faces water scarcity. Factors such as rapid population growth, urban expansion, industrial development, and unsustainable water management practices contribute to increased municipal water demand and per capita water consumption. This trend is evident in the Jubail Industrial City (JIC), the largest industrial city in the Middle East. Although JIC heavily relies on desalination and groundwater extraction to meet growing water needs, it lacks a strategic vision for water conservation. The objective of this paper is to identify the causes of water scarcity, assess the sustainability of current water management practices, and develop a sustainable water conservation strategy using JIC as a case study. The study adopts a mixed-method approach, involving a comprehensive review of literature and official documents, along with an analysis of successful case studies of water conservation practices in arid regions worldwide. The proposed strategy encompasses demand management, adoption of water-efficient technologies, water reuse and recycling, public awareness and education, and policy and governance frameworks. Strategic water conservation, optimization and reuse hold significant relevance to industry settings. The study’s findings can contribute to the enhancement of the municipal water supply sector and support decision-makers in achieving the sustainable water resource management goals outlined in Saudi Vision 2030.

High water use plants influence green roof substrate temperatures and their insulative benefits

Green roofs are amongst the solutions employed to deliver sustainable buildings in cities. Their vegetation and substrate layers can reduce the heat transfer through the roof, thus potentially reducing energy used for building cooling and heating. However, little research has investigated the insulative properties of drought-tolerant plants which also have high water use. These plants have been found to improve runoff retention by removing larger volumes of water from the substrate through higher transpiration rates than succulents. This planting strategy may also enhance green roof cooling performance due to their greater evapotranspiration rates.In this study, the thermal performance of three drought-tolerant species with high water use — Lomandra longifolia, Dianella admixta, and Stypandra glauca — was evaluated and compared with a commonly used succulent species (Sedum pachyphyllum) and a bare unplanted module.L. longifolia had the best insulative performance during the entire investigated period, reducing green roof substrate surface temperature up to 1.86 °C compared to succulent S. pachyphyllum. In summer, the mixture reduced heat gain to a greater extent than monoculture plantings of all species except L. longifolia. Summer measurements also suggest that plants with high leaf area index (LAI) and higher albedo should be selected to reduce surface temperatures. High evapotranspiration rates of high water use L. longifolia led to greatest reduction of bottom surface temperatures during a heatwave when decreasing its water content from 18.5% to 2.9%. Results obtained using an analytical hierarchical partitioning technique indicated air temperature had the most significant impact on temperatures at both the surface of the planting substrate and the bottom of each green roof unit, accounting for 48% to 58% of the variation.

Mapping of Evapotranspiration and Determination of the Water Footprint of a Potato Crop Grown in Hyper-Arid Regions in Saudi Arabia

Seasonal quantification of a crop’s evapotranspiration (ET) and water footprint (WF) is essential for sustainable agriculture. Therefore, this study was conducted to estimate the ET and WF of an irrigated potato crop using satellite imagery of Landsat and Sentinel-2 sensors. The Simplified Surface Energy Balance (SSEB) algorithm was used to evaluate the crop water use (ETa) for potato fields belonging to the Saudi Agricultural Development Company, located in the Wadi-Ad-Dawasir region, Saudi Arabia. Normalized difference vegetation index (NDVI), soil-adjusted vegetation index (SAVI), and land surface temperature (LSD) were computed for Landsat and Sentinel-2 datasets, which were used as inputs for mapping the potato tuber yield and, subsequently, the WF. The results indicated that the NDVI showed the best accuracy for the prediction of the potato tuber yield (R2 = 0.72, P &gt; F = 0.021) followed by the SAVI (R2 = 0.64, P &gt; F = 0.018), compared to the field harvested actual yield (YA). A comparison between the satellite-based ETa and the actual amount of water applied (WA) for irrigation showed a good correlation (R2 = 0.89, RMSE = 4.4%, MBE = 12.9%). The WF of the potatoes in the study area was estimated at values between 475 and 357 m3 t−1 for the early (September–December) and late (December–April) growing periods, respectively. A major portion (99.2%) of the WF was accounted for from irrigation with variations of 18.5% and 3.5% for early- and late-planted potatoes, respectively, compared to the baseline (crop planted in season). In conclusion, the results showed the possibility of satisfactorily estimating the WF using the SSEB algorithm by integrating the Landsat-8 and Sentinel-2 datasets. In general, the high rates of ET in the early planting season led to higher WF values compared to the in-season and late planting dates; this will help in selecting suitable planting dates for potato crops in the study area and areas with similar environments, which enhances the opportunities for sustainable management of irrigation water.

Investigating the effectiveness of Landsat-8 OLI and Sentinel-2 MSI satellite data in monitoring the effects of drought on surface water resources in the Western Cape Province, South Africa

Drought frequency and magnitude are increasing, posing significant risks to surface water bodies, particularly in arid and semi-arid regions. Leveraging on moderate resolution satellite data, such as Landsat-8 Operational Land Imager (OLI) and Sentinel-2 MultiSpectral Instrument (MSI), offers unique opportunities for monitoring surface water availability and drought impacts. In this study, we assessed the extent to which Landsat-8 OLI and Sentinel-2 MSI satellite data can be used to characterise and monitor the impacts of drought on water resources in the Western Cape, South Africa. Multispectral indices including Normalised Difference Vegetation Index (NDVI), Vegetation Condition Index (VCI), Normalised Difference Water Index (NDWI), Modified Normalised Difference Water Index (MNDWI), and the Land Surface Water Index (LSWI+5) were computed to determine the most suitable method for surface water detection and drought monitoring. Sentinel-2-derived NDVI emerged as the most suitable index for mapping surface waterbodies, demonstrating an overall accuracy of 77.27%. However, LSWI+5 exhibited limitations, misclassifying built-up and mountainous areas as surface waterbodies. SPI, VCI, and WRSI effectively identified drought periods and correlated well with climate data, revealing low rainfall and high evapotranspiration rates during the 2016–2018 drought period. These findings provide valuable insights into surface water variability and the impacts of drought on water resources. Overall, our study underscores the feasibility of utilizing moderate resolution datasets to assess drought impacts on surface water resources, enabling improved water resource management, drought detection, and preparedness efforts in resource limited environments.

Comparative study on seasonal variations in physico-chemical characteristics of four soda lakes of Ethiopia (Arenguade, Beseka, Chitu and Shala)

Soda lakes are productive natural ecosystems with substantial economic and non-economic values. Currently, they are facing considerable environmental threats that can lead to further degradation. The objective of this study was to investigate comparative spatiotemporal variations of physicochemical properties of four Ethiopian soda lakes in comparison with their historical data. Central (open-water) sampling sites were selected from four Ethiopian soda lakes: Arenguade, Beseka, Chittu and Shala. Water samples were collected from open sampling stations from January to December 2020 and analyzed at Limnology laboratory of Addis Ababa University. The geographical position of each lake was determined by means of Global Positioning System (GPS). All physicochemical factors exhibited significant differences between seasons (ANOVA, P < 0.05), except salinity in Lake Shala. The concentrations of physicochemical parameters were generally high during the dry seasons in the studied lakes due to the low incidence of rainfall, caused by recurrent drought, resulting in higher evapotranspiration rates as they are characterized by a long dry season. Lakes Arenguade and Beseka showed considerable decrease in conductivity, alkalinity and salinity, compared to data from the 1960s and 1990s, which might be attributed to dilution effect. The same parameters show slightly increasing trend in Lake Arenguade which might be due to high evaporation rate. In general, the physicochemical parameters of the study lakes showed temporal variations, which could be attributed to the dilution effect, evaporation, and hydrological characteristics of the Ethiopian Rift Valley. In the face of climate change and recurring droughts, in the Ethiopian Rift Valley, the outcomes of this study might be used as input for the long-term planning, of water resources management and devising mitigation strategies.

Evaluation of perennial reference evapotranspiration (ETo) over a typical dryland using satellite images: A case study from Uzbekistan

Evapotranspiration (ET) is one of the most significant compartments in the energy and water balance between the atmosphere and the Earth's surface. Global climate change has an impact on the water cycle and can result in an increase in ET from the land surface; nevertheless, an increase in ET can destabilize the macro- and micro-climate at the local and continental levels. In line with this, the purpose of this article is to learn more about the factors that contribute to the high and current reference ET (ETo) rate of Karakalpakstan (Uzbekistan). MODIS Terra images was used to analyze long-term land cover change. The Google Earth Engine code editor, Erdas Imagine 2020, and ArcMap 10.8 were used to map land cover change and the leaf area index (LAI). Though the Normalized Difference Vegetation Index and the Soil-Adjusted Vegetation Index were used because of their past performance as affirmative measurement techniques for vegetation monitoring. The Hargreaves-Samani equation was utilized to ETo in this study. Increased crop density in agriculture and the conversion of barren soil to grasslands to rehabilitate the seashore ecosystem of the Aral Sea influenced LAI significantly, according to multifactorial analyses of perennial air temperature, land cover change, solar irradiance, and ETo in a typical dryland of Uzbekistan. However, the extension of LAI in the agricultural area of Karakalpakstan substantially accelerated the ETo rate, which was a key contributor of an increase in crop water demand. We can see that measured solar radiation and ETo were consistent across time by looking at the nearly same quantities for both. As a result, we assume that global climatic changes have no effect in the uncertainty of solar radiation and ET rate.

Assessing the role of evapotranspiration in reducing surface temperatures in Harare using the SEBAL algorithm

Within urban areas, buildings, roads, and paved surfaces, absorb and re-emit the sun's heat more than natural landscapes. Urban areas, where these structures are highly concentrated and vegetation is limited, become ‘heat islands’ contributing to a range of environmental, economic, and human health problems. Despite this, limited research, has, to date, been carried out to assess the influence of evapotranspiration (ET) on urban surface temperatures for Harare, Zimbabwe. In this study, the uSEBAL algorithm was used to estimate evapotranspiration (ET) and land surface temperature (LST) using Landsat images in Hazare, Zimbabwe. The influence of ET on LST was also examined during the hot and post rain seasons. Results showed significant negative relationships (p < 0.05) between ET and LST. High ET rates were recorded over water bodies and green spaces as compared to built-up areas. High ET rates resulted in correspondingly low LST. This is the first time such results are reported for Harare. The conclusion drawn from these results is that as ET increases, temperature decreases, thus there was a negative relationship between ET and LST during the hot season. Additionally, low ET coincided with high LST in low vegetation and densely built-up areas. From these findings we can deduce ways of mitigating effects of thermal discomfort in urban areas i.e., inclusion of green spaces and water bodies within the cities. It is recommended that more green spaces be created within residential zones and encourage construction of green buildings and cooling technologies.