High Potential Evapotranspiration Research Articles

Comprehensive Analysis of the NOAA National Water Model: A Call for Heterogeneous Formulations and Diagnostic Model Selection

AbstractWith an increasing number of continental‐scale hydrologic models, the ability to evaluate performance is key to understanding uncertainty and making improvements to the model(s). We hypothesize that any model, running a single set of physics, cannot be “properly” calibrated for the range of hydroclimatic diversity as seen in the contenintal United States. Here, we evaluate the NOAA National Water Model (NWM) version 2.0 historical streamflow record in over 4,200 natural and controlled basins using the Nash‐Sutcliffe Efficiency metric decomposed into relative performance, and conditional, and unconditional bias. Each of these is evaluated in the contexts of meteorologic, landscape, and anthropogenic characteristics to better understand where the model does poorly, what potentially causes the poor performance, and what similarities systemically poor performing areas share. The primary objective is to pinpoint traits in places with good/bad performance and low/high bias. NWM relative performance is higher when there is high precipitation, snow coverage (depth and fraction), and barren area. Low relative skill is associated with high potential evapotranspiration, aridity, moisture‐and‐energy phase correlation, and forest, shrubland, grassland, and imperviousness area. We see less bias in locations with high precipitation, moisture‐and‐energy phase correlation, barren, and grassland areas and more bias in areas with high aridity, snow coverage/fraction, and urbanization. The insights gained can help identify key hydrological factors underpinning NWM predictive skill; enforce the need for regionalized parameterization and modeling; and help inform heterogenous modeling systems, like the NOAA Next Generation Water Resource Modeling Framework, to enhance ongoing development and evaluation.

Multivariate regression trees as an “explainable machine learning” approach to explore relationships between hydroclimatic characteristics and agricultural and hydrological drought severity: case of study Cesar River basin

Abstract. The typical drivers of drought events are lower than normal precipitation and/or higher than normal evaporation. The region's characteristics may enhance or alleviate the severity of these events. Evaluating the combined effect of the multiple factors influencing droughts requires innovative approaches. This study applies hydrological modelling and a machine learning tool to assess the relationship between hydroclimatic characteristics and the severity of agricultural and hydrological droughts. The Soil Water Assessment Tool (SWAT) is used for hydrological modelling. Model outputs, soil moisture and streamflow, are used to calculate two drought indices, namely the Soil Moisture Deficit Index and the Standardized Streamflow Index. Then, drought indices are utilised to identify the agricultural and hydrological drought events during the analysis period, and the index categories are employed to describe their severity. Finally, the multivariate regression tree technique is applied to assess the relationship between hydroclimatic characteristics and the severity of agricultural and hydrological droughts. Our research indicates that multiple parameters influence the severity of agricultural and hydrological droughts in the Cesar River basin. The upper part of the river valley is very susceptible to agricultural and hydrological drought. Precipitation shortfalls and high potential evapotranspiration drive severe agricultural drought, whereas limited precipitation influences severe hydrological drought. In the middle part of the river, inadequate rainfall partitioning and an unbalanced water cycle that favours water loss through evapotranspiration and limits percolation cause severe agricultural and hydrological drought conditions. Finally, droughts are moderate in the basin's southern part (Zapatosa marsh and the Serranía del Perijá foothills). Moderate sensitivity to agricultural and hydrological droughts is related to the capacity of the subbasins to retain water, which lowers evapotranspiration losses and promotes percolation. Results show that the presented methodology, combining hydrological modelling and a machine learning tool, provides valuable information about the interplay between the hydroclimatic factors that influence drought severity in the Cesar River basin.

Performance and uncertainties of five popular satellite-based precipitation products in drought monitoring for different climate regions

Satellite-based precipitation products (SPPs) can provide crucial precipitation estimations for large-scale, near-real-time meteorological drought monitoring. However, the performances and uncertainties of SPPs in capturing drought information may vary greatly by product and climate region and are still poorly understood. In this study, we comprehensively evaluated the accuracy of five popular SPPs (MSWEP, TMPA 3B42, PERSIANN-CDR, CHIRPS, and COMRPH) in characterizing meteorological drought in mainland China. (1) Under global warming conditions, the standardized precipitation evapotranspiration index (SPEI) identified a significant decrease in drought associated with higher potential evapotranspiration (PET), which indicated the essential role of PET in determining drought evolution over different climate regions. (2) Among all the SPPs investigated, MSWEP, TMPA 3B42, and PERSIANN perform best in capturing the spatiotemporal pattern of the SPEI trend in the arid Tibetan Plateau regions, transition regions, and humid regions, respectively. In terms of drought category and drought characteristics, MSWEP and TMPA 3B42 perform very well for humid regions, and CHIRPS is better for cold and arid regions, with the poorest performance being found in CMORPH. However, no product performs well for all climate regions for drought monitoring. (3) The optimized parameters (OPs) are the dominant factor for drought uncertainties, followed by the interaction effect and SPPs, with great regional dependence. The OPs contributed the most to drought uncertainties over the relatively arid area of northern China, the interaction of OPs and SPPs did so in the humid area of China, and SPPs were found to contribute the most in the central Tibetan Plateau and some parts of humid regions. Our findings provide guidelines on the choice and application of existing SPP datasets for drought monitoring in different climate zones, as well as some clues to further improve the products over areas where they perform poorly.

Modelling groundwater recharge, actual evaporation, and transpiration in semi-arid sites of the Lake Chad basin: the role of soil and vegetation in groundwater recharge

Abstract. The Lake Chad basin, located in the centre of northern Africa, is characterized by strong climate seasonality with a pronounced short annual precipitation period and high potential evapotranspiration. Groundwater is an essential source for drinking-water supply, as well as for agriculture and groundwater-related ecosystems. Thus, assessment of groundwater recharge is very important although also difficult because of the strong effects of evaporation and transpiration, as well as the limited available data. A simple, generalized approach, which requires only limited field data, freely available remote sensing data, and well-established concepts and models, is tested for assessing groundwater recharge in the southern part of the basin. This work uses the FAO dual-Kc concept to estimate E and T coefficients at six locations that differ in soil texture, climate, and vegetation conditions. Measured values of soil water content and chloride concentrations along vertical soil profiles together with different scenarios for E and T partitioning and a Bayesian calibration approach are used to numerically simulate water flow and chloride transport using Hydrus-1D. Average groundwater recharge rates and the associated model uncertainty at the six locations are assessed for the 2003–2016 time period. Annual groundwater recharge varies between 6 and 93 mm and depends strongly on soil texture and related water retention and on vegetation. Interannual variability of groundwater recharge is generally greater than the uncertainty of the simulated groundwater recharge.

Proteomic Analysis of Maize Cultivars Tolerant to Drought Stress

Maize is a crop of significant economic importance. In the northeast region of Brazil, it serves as the foundation of family support for the majority of farmers. However, achieving high levels of productivity requires an adequate water supply throughout its growth cycle. The northeast semi-arid region experiences low rainfall and high potential evapotranspiration, directly affecting maize development and leading to severe declines in productivity. In this study, genetic selection and proteomic analysis are proposed as a strategy to identify the tolerance of maize cultivars against water stress. The experiments were conducted under two water regimes using randomized block designs with three replicates. Development and productivity traits were evaluated, and genetic parameters were estimated using mixed linear models. Selection for water stress tolerance was based on the harmonic mean of the relative performance of genotypic values. Total protein extraction from maize leaves followed the protocol established by the phenol method, and peptides were analyzed through mass spectrometry. The AG8677P cultivar demonstrated remarkable productivity under drought stress conditions, and proteins related to various fundamentally important biological processes for the tolerance mechanism were identified. The combination of genetic selection with proteomic analysis proves to be an efficient strategy, even in the face of limited resources and a small number of treatments.

Groundwater Recharge and Circulation in Dolomitic Aquifer Located in Semi-Arid Region: Evidence from the δ18O and δ2H Record, South Africa

Dolomitic aquifers are regarded as important groundwater storage sites in South Africa. Since these aquifers occur in a semi-arid climatic setting with low rainfall, often characterized by a torrential downpour and high potential evapotranspiration, the occurrence of active recharge is very limited (<5% of mean annual rainfall) as compared with the rainfall amount. The Malmani dolomites that have undergone greenschist metamorphism contain widespread caves and open karst structures at shallow levels, which facilitate groundwater recharge, circulation, storage and spring occurrence. However, the open karst structures receive recharge that passes through fractures in the vadose zone, which regulates the recharge through retardation and mixing processes. The integrated approach involving major ions and stable isotopes of water was applied to understand the recharge mechanism. The cave drip water samples were represented by the δ18O values of −3.95‰ to 3.32‰ and the δ2H values ranging from −11.0‰ to 27.7‰. On the other hand, the rainfall isotope results for δ18O fall between −16.11‰ and 5.38‰, while the δ2H values fall between −105.7‰ and 35.6‰. The most depleted Malapa springs contain δ18O of −5.64‰ and δ2H of −32.4‰. Based on the results, the mixing of water in the vadose zone could be considered as an indicator of the dominance of a slow-diffusive flow process in the aquifer as a result of poor fracture permeability. However, regional groundwater circulation through faults and dykes besides interconnected karst structures helps in generating highly productive karst springs in the region characterized by low rainfall.

Assessing the response of vegetation photosynthesis to flash drought events based on a new identification framework

Flash drought events pose serious threats to terrestrial ecosystems due to their rapid intensification. However, the comprehensive assessment of recovery stage in flash drought is hindered by the insufficient consideration of reduplicative decline in soil moisture. Besides, how the vegetation photosynthesis respond to flash drought remains unknown. Here, a new method for explicitly characterizing flash drought events was proposed, incorporating both development rate and duration, with particular emphasis on the process of soil moisture change during the recovery stage. Then the temporal and spatial evolutions of the flash drought over the Pearl River Basin were analyzed. Solar-induced chlorophyll fluorescence (SIF) was used to explore the responses of different vegetation types to flash drought. The results indicated that the onset speed may be increasing, and the flash drought in 2007 was quite serious. Most flash drought events lasted 32 to 48 days. Besides, this study focused on the response of forests, grasslands and crops to flash drought, and the forestlands were less sensitive to flash droughts, while croplands experienced the most flash drought events, and the time of photosynthesis loss of croplands was the shortest. Moreover, precipitation deficit, high temperature, high evapotranspiration (ET) and high potential evapotranspiration (PET) were the main driving factors triggering flash drought. The soil moisture was above 40th percentile after the end of a flash drought, which demonstrate the accuracy of the framework in identifying the development of flash drought in the concern area. Our findings also demonstrated the great effectiveness of SIF in monitoring the resistance of ecosystems, deepening our understanding of the response of vegetation photosynthetic capacity to flash drought events.

Ecological factors affecting the recent Picea abies decline in Slovenia: the importance of bedrock type and forest naturalness

Norway spruce (Picea abies [L.] Karst.) has been at the centre of controversy for many decades. Recent evidence of its profound disturbance-induced damage and consequent stock depletions across forest landscapes in Europe has reinforced doubts regarding the sustainability and prospects of this tree species in the future. Like many other European countries, Slovenia has experienced significant Norway spruce mortality and a decrease in growing stock primarily as the result of several disturbance agents (bark beetle outbreaks, an ice storm, windthrows). We investigated a countrywide spruce growing stock decline based on data between 2010 and 2018. Particular focus was placed on identifying the main ecological drivers of this decline, namely geological conditions, climatic parameters, soil attributes, topographic factors and forest stand characteristics. The effects of potential predictors on the relative change (%) in spruce volume (m3 ha-1) during the period 2010-2018 were analysed with Generalized Additive Models. Based on a national dataset including forest compartments (n = 6355) with a spruce growing stock decline > 10%, we found mixed support for ecology-based hypotheses. While spruce decline responded to bedrock type as predicted (i.e., greater relative decline in carbonate compared to silicate compartments), higher forest naturalness (preservation of tree species composition) was not associated with a lower decline. Spruce decline was amplified by higher potential evapotranspiration and soil clay content but showed a strong negative relationship with spruce proportion in the year 2010. General trends along the gradients of other selected predictors (stoniness/rockiness and heat load index) were less pronounced. The results suggest that most of these ecological predictors interact with geology and forest naturalness in affecting Norway spruce decline. Our analysis reveals that bedrock type can play an important role due to its mitigating effects. However, forest naturalness is of secondary significance as intensified large-scale forest disturbances likely override its buffering potential.

Spatiotemporal variation of potential evapotranspiration and meteorological drought based on multi-source data in Nepal

Quantifying the spatiotemporal dynamic of potential evapotranspiration (PET) in topographically complex country are often limited by the scarcity and difficulty in obtaining ground-based measured climate data. Remote sensing products have multiple advantage, which allows rapid acquisition of information and status over large areas and long time series. This study compared and explored the spatiotemporal variation of PET across Nepal using three widely-used remote sensing and reanalysis data PET products (CRU_PET, MODIS_PET and PML_PET), and PET estimation using Hargreaves-Samani method based on CHIRTS datasets. On the basis of this, the spatiotemporal dynamic at seasonal and annual level and the periodical change of PET and meteorological aridity index AI (precipitation P/PET) were identified using Mann-Kendall test and Morlet Wavelet method. These PET products showed general spatial consistency over most areas in Nepal with higher PET in the south and less in the north. However, great differences were also found in PET values for four different products. Compared with the three remote sensing and reanalysis data products, CHIRTS_PET performs better in Nepal. The AI based on CHIRTS_PET showed an insignificant increasing (wetting) trend in the western and southern regions, while an insignificant decreasing (drying) trend in the central and northeastern region, which is generally consistent with the spatial pattern of precipitation. In the western and southern regions, the positive impact of increasing precipitation on AI masked the negative effect of increasing PET, and thus making this region getting humid. However, in the central and northeastern region, the increase in PET aggravates the impact of reduced precipitation on the drying trend. Our investigation have broad implications for sustainable water resources management under climate change in a topographically complex country like Nepal.

A biome-dependent distribution gradient of tree species range edges is strongly dictated by climate spatial heterogeneity.

Understanding the causes of the arrest of species distributions has been a fundamental question in ecology and evolution. These questions are of particular interest for trees owing to their long lifespan and sessile nature. A surge in data availability evokes a macro-ecological analysis to determine the underlying forces limiting distributions. Here we analyse the spatial distribution of >3,600 major tree species to determine geographical areas of range-edge hotspots and find drivers for their arrest. We confirmed biome edges to be strong delineators of distributions. Importantly, we identified a stronger contribution of temperate than tropical biomes to range edges, adding strength to the notion that tropical areas are centres of radiation. We subsequently identified a strong association of range-edge hotspots with steep spatial climatic gradients. We linked spatial and temporal homogeneity and high potential evapotranspiration in the tropics as the strongest predictors of this phenomenon. We propose that the poleward migration of species in light of climate change might be hindered because of steep climatic gradients.

Climate Seasonality Mediates Global Patterns of Foliar Carbon and Nitrogen Isotopes

Frequent extreme climate events have significantly affected plant intrinsic water-use efficiency (iWUE) and forest nitrogen (N) availability. Understanding the coupling between climate seasonality and plant water, carbon, and nitrogen may provide insights into how plants respond to climate change. Here, we integrated Δ13C and δ15N in woody plant leaves as a probe to elucidate the iWUE and N availability patterns of plants under global change and found that woody plants from sites with high climate seasonality, especially precipitation seasonality, tend to have improved iWUE and N availability compared with those with low seasonality. Specifically, high potential evapotranspiration, solar radiation, vapor pressure deficit, and low precipitation during the growth season are the driving factors. The intra-annual and annual climate explained 43% and 49% of Δ13C and 40% and 53% of δ15N, respectively, suggesting that the intra-annual climate is at least as important as the annual climate. These results suggest that not only the direction (decrease vs. increase) of decadal climate should be counted but also the abnormal fluctuation of intra-annual should be considered. Climate seasonality is a more suitable ecological filter for determining plant distribution across terrestrial ecosystems.

Ecological niche modelling of Cantharellus species in Benin, and revision of their conservation status

Of the eight Cantharellus species known from Benin, seven have been encountered under similar macroecological conditions. The present work attempts to generate a more complete distribution of these seven species. Forty-eight occurrences of the target species and four explanatory variables including three bioclimatic variables and a land cover variable were used to build an ensemble model from five modelling approaches under the Biomod2 package of R software. Results showed a distribution restricted to the Bassila and Atacora mountain range phytogeographic districts with excellent statistical performance (TSS = 0.98, AUC = 0.99). This distribution is governed mainly by high soil moisture and high potential evapotranspiration, thus defining only gallery forests as the most suitable habitat for chanterelles in Sudano-guinean and Soudanese ecozones of Benin. Based on IUCN criterion B1 and sub-criteria B1a and B1c(i), these seven species were categorized under the Endangered (EN) threat category according to our results.

Climatic Water Balance and Groundwater Recharge in Abu-Jir Village, Al-Anbar Governorate, Western Iraq

The study area is located in Al-Anbar Governorate, western Iraq. The climatic data were collected from Al-Ramadi Meteorological Station for the period 1990 to 2020 and used to assess the climatic condition of the study area. The total annual rainfall, relative humidity, monthly average temperature, evaporation, wind speed and sunshine duration are 108 mm, 52.7 %, 22.6˚C, 2814.3 mm, 2.2 m/s and 8.8 h/day, respectively. The climate of the study area is described as an arid to sub arid and relatively hot in summer and cold with low rain in winter. During the data used, the highest potential evapotranspiration was 217.1 mm in July, while the lowest value was 10.7 mm in January, with a total amount of 1170.07 mm. The highest and lowest corrected evapotranspiration becomes 264.2 mm in July and 9.4 mm in January, with 1310.3 mm. water Surplus (WS) is 2.1mm, 10.71mm, and 5.65mm in December, January and February, respectively. The WS was 18.46mm, forming 17.09 % of the total annual rainfall. The groundwater recharge (18.46 mm) with a rate of 17.09% represents the recharge from the total rainfall zero surface runoff. It has been found that the low amount of rain and sandy soil are among the most important factors causing the absence of surface runoff.

Climate and landscape variation shapes the water balance of piñon pine-juniper woodlands

• Piñon pine-juniper woodlands are strongly influenced by water balance (WB) variation. • Southern Nevada woodlands are a model for future hot and dry conditions regionally. • WB magnitude was driven by climate; partitioning was shaped by landscape factors. • Tree transpiration partitioning and magnitude declined at moderate woodland densities. • Climate conditions and stand characteristics impart meaningful WB variation. Piñon pine-juniper woodlands are strongly influenced by water balance variation imparted by variation in climate, landscape attributes, and tree stand characteristics. To elucidate how these multiple factors shape woodland ecohydrology, we simulated the water balance of woodlands in the Spring (higher precipitation (PPT), higher potential evapotranspiration (PET)) and Sheep (lower PPT, lower PET) mountains of southern Nevada, USA. Simulations included: (1) elevation and climate (2000, 2200 and 2400 m; 3 scenarios); (2) low and moderate adult tree density (2 scenarios); and (3) south-facing, neutral, and north-facing aspects (3 scenarios; 18 scenarios in each mountain range). Due to the interplay between PPT and PET, the lower PPT Sheep mountains were atmospherically less dry (PPT – PET) than the Spring mountains. Following this, the Sheep mountains had higher transpiration partitioning into evapotranspiration (T/ET), whereas transpiration magnitude was higher in the Spring mountains. In both mountain ranges, soil moisture and tree transpiration were highest in winter and spring, and low in summer. T/ET was maximized at 12–15 m 2 ha − 1 basal area, illustrating the increasing influence of interception at higher tree densities. Thus, the water balance of these woodlands was driven by PPT, yet partitioning was shaped by PET and tree stand density. Interplay between soil moisture, tree transpiration, evaporation and interception is a defining characteristic of woodlands in southern Nevada, and may be influenced at broader and finer spatial scales. Better understanding of climatic, landscape, and tree stand factors may help to explain high water balance variation observed in woodlands across the western US, and improve understanding of how future change to piñon pine-juniper ecosystems may be realized.

Characterization and Classification of Pigeon Pea Growing Soils and their Land Suitability for Hot Semiarid Deccan Plateau, India

Background: Semiarid lands possess limitations of climate such as low and erratic rainfall, long dry spell, high potential evapotranspiration and lesser length of growing period which directly influence the yield and productivity of crop along with the soil properties. Pigeon pea, being one of the most dominant pulse crops cultivated in the semiarid Deccan plateau, an understanding on the soils where pigeon pea is mainly grown and the evaluation of their land suitability was found to be essential. Methods: Land resource inventory at 1:10,000 scale was carried out in Mahabubnagar Rural mandal, Mahabubnagar district, Telangana state of South Deccan plateau to characterize the major pigeon pea growing soils and their land suitability evaluation. Result: When the entire study area was evaluated for its suitability, majority of the area (32.79%) was marginally suitable, followed by moderately suitable area (16.24%) with moderate to severe limitations of nutrient availability, rooting conditions, gravelliness and texture and a very small area of 5.55 per cent was found to be highly suitable towards the crop. Out of the 18 soil series identified, only five were the major pigeon pea soils which were mostly marginally suitable (S3) with limitations of nutrient availability, slope, effective root depth and texture. Though the climatic characteristics of the area were highly favourable to the crop classified under the highly suitable class (S1), rooting conditions, nutrient availability and slope were the major limitations towards the cultivation and productivity of pigeon pea.

Does forest management affect the magnitude and direction of the afforestation effect on soil methane fluxes? A meta-analysis

Evidence suggests that tree plantations change soil methane (CH4) fluxes (magnitude and/or direction of the fluxes) compared to herbaceous land (i.e. afforestation effect) due to the effect of trees increasing methanotroph bacteria abundance and enhancing soil gas diffusivity. However, the magnitude of this afforestation effect is highly variable across studies. Here, we evaluated whether the variation in the afforestation effect depends on forestry management strategies, described by stand age and density, as well as taxonomic identity of the tree species, and the interaction with climatic conditions. To this end, we conducted a meta-analysis using 47 paired samples of afforested and contiguous herbaceous land from 14 studies located in different biomes worldwide. We found that afforestation predominantly increases the capacity of soil net CH4 uptake (i.e. more negative fluxes) compared to herbaceous land, but the magnitude of this effect was highly heterogeneous across paired samples. This heterogeneity was explained by environmental conditions, but significant effects of forest stand age and density were also found proving the importance of forest management on this ecological service. Soil net CH4 uptake following afforestation increases with increasing stand age. Although the stand stocking effect could be tested with a limited number of studies (24 out of the 47 paired samples), the results suggest that net CH4 uptake decreases with tree stocking (stand density) in the range of values up to 1500 individuals per ha. No change in CH4 fluxes was observed above this high stand density. Contrary to our expectations, no effect of taxonomic identity of the trees considering the most planted genera (Pinus and Eucalyptus) was observed in the average soil CH4 fluxes. Furthermore, a significant correlation between the afforestation effect on soil water content and CH4 flux suggests that the most plausible cause of the increased soil net CH4 uptake is driven by the forest impact on soil desiccation, which in turn increases in sites with higher water limitation (i.e. higher potential evapotranspiration and high temporal rainfalls variations within the ranges of the available studies). Finally, our study provides evidence that by modifying rotation time and stand stocking, afforested land may increase its environmental service as a sink of atmospheric CH4.

Causes of changes in actual evapotranspiration and terrestrial water storage over the Eurasian inland basins

AbstractThe climate of the Eurasian inland basins (EIB) is characterized by limited precipitation and high potential evapotranspiration, making water storage in the EIB vulnerable to global warming and human activities. There is increasing evidence regarding varying trends in water storage across different regions; however, a consistent conclusion on the main attributes of these trends is lacking. Based on the hydrological budget in a closed inland basin, the main attributes of changes in actual evapotranspiration (AET) and terrestrial water storage (TWS) were identified for the EIBs and each closed basin. In the EIB and most of its closed basins (13/16), the TWS and AET showed significantly decreasing and non‐significant increasing trends, respectively. The primary cause underlying the significantly decreasing TWS in the EIB was the increase in AET. Approximately 70% of the increase in AET was attributed to increased irrigation diversions from groundwater and glacial melt runoff. At the basin scale, similar to the EIB, changes in AET were the predominant factor driving changes in TWS in most basins, with the exception of the Balkhash Lake basin (BLB), Iran inland river basin (IIRB), Qaidam basin (QB) and Turgay River basin (TuRB). In these basins, changes in precipitation largely contributed to the TWS changes. The AET consumption of other water resources was the main factor contributing to AET changes in seven of the 16 basins, including the Aral Sea, Caspian Sea, Junggar, Monglia Plateau, Qiangtang Plateau and Tarim River basins. The increase in precipitation contributed more than 60% of the increasing AET in four of the 16 basins, particularly in the Helmand River basin and QB (>90%). Changes in precipitation and consumption by other water supply sources contributed to approximately half of the AET changes in the other five basins, including the Inner Mongolia Plateau basin, Issyk‐Kul Sarysu basin, BLB, IIRB and TuRB.

Temperature, not precipitation, drives the morphological traits of Didymodon rigidulus in Tibet

Plant traits reflect the response and adaptation of plants to environmental changes and play important roles in the prediction of the effects of different environmental conditions on plants and plant-mediated processes. However, few studies have focused on the traits of nonvascular plants, such as bryophytes, although such plants are important participants in the primary productivity and biogeochemistry in harsh environments. In this study, the adaptive morphological traits and their interactions in the moss species that adapt to harsh and acute changeable environment were determined. Environmental factors that drive the changes in these traits were also evaluated. A total of 43 specimens of Didymodon rigidulus were collected from 38 sampling sites in arid and semi-arid regions in Tibet. Twelve morphological traits were investigated by microscope measurement, and then their interrelations and relations to environmental variables were quantified by employing Spearman’s correlation analysis, hierarchical partitioning analysis, and partial least squares path modeling. Results showed that along with the environmental gradient, the plant height, leaves, and cells of D. rigidulus had changed significantly, and these parameters were largely interpretable in functional and adaptive terms. The lower the mean annual temperature (MAT) was, the thicker was the surface cell wall and the wider was the cell cavity of D. rigidulus. The higher potential evapotranspiration (PET) was, the thicker was the surface cell wall but the smaller were the leaves. MAT and PET were the main driving forces for the development of such traits of D. rigidulus. These results provide important insight into the adaptive syndrome of nonvascular plants associated with stress tolerance in the varied and harsh environment in Tibet. This study indicated the importance of considering the effects of climate change, especially the warming temperature on species adaption and community assemblage.

Thornthwaite Models for Estimating Potential evapotranspiration in Medan City

Evapotranspiration plays a big role in the hydrology process. Potential Evapotranspiration (PET) always keeps soil moisture available, although an amount of water evaporates through evaporation and transpiration. The Thornthwaite equation uses air temperature and latitude from meteorological observations for estimating PET. Medan City is one of the biggest cities in Indonesia that have a problem with land-use change that affected water balance. This study is to estimate the PET and to learn the water balance in Medan City. The monthly temperature data for the period 2011-2020 is collected from three meteorological stations for estimating PET using the Thornthwaite equation. The highest monthly temperature is in Belawan Maritime Meteorological Station yet the lowest rainfall. The trends of PET depend on the month. The highest PET in Jan.-Apr. and Sep.-Dec. are in Belawan Maritime Meteorological Station, while the highest PET in May-Aug. is in Indonesia Agency for Meteorology Climatology and Geophysics Region I Medan. The P-PET has shown negative and positive values. The lowest P-PET is found in Belawan Maritime Meteorological Station in March and the highest P-PET is found in Indonesia Agency for Meteorology Climatology and Geophysics Region I Medan in October.

Nitrate Transport and Retention in Western European Catchments Are Shaped by Hydroclimate and Subsurface Properties

AbstractExcess nitrogen (N) from anthropogenic sources deteriorates freshwater resources. Actions taken to reduce N inputs to the biosphere often show limited or only delayed effects in receiving surface waters hinting at large legacy N stores built up in the catchments' soils and groundwater. Here, we quantify transport and retention of N in 238 Western European catchments by analyzing a unique data set of long‐term N input and output time series. We find that half of the catchments exhibited transport times with an average riverine concentration peak arriving 5 years after application. Longer transport times were evident in catchments with high potential evapotranspiration and low precipitation seasonality. On average the catchments retained 72% (Interquartile Range: 18%) of the N from diffuse sources with retention efficiency being specifically high in catchments with low discharge and thick, unconsolidated aquifers. The estimated transport time scales do not explain the observed N retention, suggesting a dominant role of biogeochemical legacy in the catchments' soils rather than a legacy store in the groundwater. Future water quality management should account for the accumulated biogeochemical N legacy by fostering denitrifying conditions or soil N recycling to avoid long‐term leaching and water quality deteriorations for decades to come.