Variation In Water Availability Research Articles

Impact of Salinity Fluctuations on Dunaliella salina Biomass Production

The utilization of microalgae as a green carbon source for chemical production has attracted attention for its potential use in sustainable and climate-friendly solutions. This study investigates the growth of Dunaliella salina, a unicellular green microalga, in response to salinity variations and water and seawater addition to compensate for evaporation in open cultures. The impact of continuous and non-continuous water addition, as well as seawater addition, on the growth of D. salina was analyzed though tank tests. The results showed that different water-addition methods did not significantly influence cell concentrations, indicating the organism’s resilience to salinity changes. Continuous water addition maintained stable salinity levels at 12%, but required continuous monitoring, while non-continuous addition reduced the intervention frequency. The overall results showed that a salinity range between 12 and 15% did not affect microalgae growth, suggesting flexibility in evaporation-loss compensation methods based on cultivation-system specifics and resource availability. Maintaining consistent biomass regardless of the water-addition method used suggests sustainable production within the tested salinity range, with seawater addition making microalgae cultivation more adaptable to regions with varying water availability. Further research, including outdoor pilot tests, is recommended to validate and extend these findings to natural environments.

The vegetation–topography heterogeneity coupling in the Loess Plateau, China

As a result of adaptation to the environment, the great environmental spatial heterogeneity leads to the high spatial heterogeneity of vegetation status. This coupling may be more apparent in water-limited drylands, where topography is the main determinant of small-scale variation in water availability and energy. Metrics describing this coupling may contribute to the detection of the extension of vegetation reshaped by human intervention and other driven forces. In this study, the heterogeneity index of coupling (HIC) was developed to indicate the coupling between spatial heterogeneity of vegetation status (Hv) and the spatial heterogeneity of topography (HT) in the Loess Plateau in northern China. The 16-day composed MODIS normalized vegetation index (NDVI) with a resolution of 250 m and SRTM DEM were employed to quantify the heterogeneity of vegetation status and the topographical heterogeneity. The results show that HIC varies among geomorphic zones, land cover types, and land cover change categories. Among all land cover types, HIC of sandy areas was the largest, followed by the HIC of the forest, shrub, farmland, and grassland. Among geomorphic zones, the highest HIC value appeared in plains with dense residential areas, followed by sandy land that is frequently reshaped by wind, rocky mountainous areas, hilly and gully loess plateaus, and loess tableland. It was revealed that the alternation of vegetation by human activities and natural disturbances shaped greater HIC. Results of this study approved the effectiveness of the HIC in reflecting the coupling of the vegetation status with topography at regional scale.

Analysis of the Growth Response of Cassava Plants (Manihot Esculenta) to Variability in Water Availability

In recent decades, there has been a very pronounced climate change on earth. Reduced rainfall and the occurrence of long droughts are direct impacts that can trigger other problems in the agricultural sector such as crop failure and weakening food security. This will also have an impact on the process of growth and agricultural production in the Lampung Province area, especially on cassava plants. Water often limits the growth and development of cultivated plants. The response of plants to lack of water can be seen in their metabolic activity, morphology, growth rate, or productivity. Cell growth is the function of plants that are most sensitive to water shortages. Lack of water will affect cell turgor so that it will reduce cell development, protein synthesis, and cell wall synthesis. The cassava clones used in this study were Garuda Clones with 5 treatment levels, namely the first treatment (P1) 0L, the second treatment (P2) 0.5L, the third treatment (P3) 1L, the fourth treatment (P4) 1.5L, the fifth treatment (P5) 2L. The result of this study is that there is a cassava growth response to water availability in each treatment except for the variable number of shoots. In the variable plant height, significant response variations are obtained, and it is known that the availability of water needed is directly proportional to the response to plant height growth that also increases.

A river runs through it: Robust automated mapping of riparian woodlands and land surface phenology across dryland regions

Riparian woodlands in drylands are critically important to human society, global biodiversity, and regional water and energy budgets. These sensitive ecosystems have experienced substantial degradation over the last several decades from climatic change and direct human activity. Nevertheless, quantifying long-term change in dryland riparian woodlands remains a major challenge, and much uncertainty exists in their remaining extent, historical breadth, and likely future trajectories. Dryland landscapes show large, fine-scale spatial heterogeneity in seasonal greenness patterns, driven in part by spatial variation in water availability. Riparian woodlands occur where water is concentrated in the landscape, either as aboveground streamflow or subsurface groundwater. In arid and semi-arid climates, this renders them phenologically distinctive from upland ecosystems. However, despite their importance and distinctiveness, there are currently no automated methods for delineating dryland riparian woodlands across regional extents in the cloud. Here we designed and implemented a cloud-based algorithm to retrieve dryland land surface phenology patterns from multispectral satellite imagery and conducted sensitivity analyses using real and simulated data to demonstrate that the approach is robust for MODIS, Sentinel-2, and Landsat over realistic ranges of noise and cloud cover. We then designed a series of random forest vegetation classifiers that integrate phenological and spectral information, vegetative structure from LiDAR, and topography from LiDAR or the Shuttle Radar Topography Mission. We implemented classifiers for three local study sites and then generalized our model to run regionally across the southwestern United States, with balanced accuracy for the riparian woodland class ranging from 94.5% to 97.5% when validated with local to regional datasets. Generally, phenological information proved more important than any other data source for mapping riparian woodlands, which showed more stability in interannual phenology than did upland vegetation types. To our knowledge, ours is the first regional, annual, automatically-generated and updated approach for mapping dryland riparian woodlands in the southwestern United States, paving the way for improved modeling and management efforts on watershed to regional scales. We also provide one of the first operational, exclusively cloud-based methods to extract dryland land surface phenology patterns using Landsat, Sentinel-2, MODIS, or other sensors, providing a framework for future studies investigating other aspects of long-term or spatial variation in dryland vegetative seasonality across the globe.

Evaluating future water availability in Texas through the lens of a data-driven approach leveraged with CMIP6 general circulation models

Climate change is escalating the frequency and intensity of extreme precipitation events, significantly influencing the spatial and temporal distributions of water resources. This is particularly evident in Texas, a rapidly growing state with a pronounced west-east gradient in water supply. This study utilizes Coupled Model Intercomparison Project Phase 6 (CMIP6) data and data-driven methodology to improve projections of Texas's future water resources, focusing on actual evapotranspiration (AET) and water availability through enhanced Multi-Model Ensembles. The results reveal that the data-driven model significantly outperforms the CMIP5 and CMIP6 models across all skill metrics, underscoring the potential of data-driven methodologies in advancing climate science. Furthermore, the study provides an in-depth analysis of the projected changes in net water availability (NWA) and estimated water demand for different regions in Texas over the next six decades from 2015 to 2074, which reveal fluctuating patterns of water stress, with the regions (nine out of sixteen water planning regions in Texas, especially for the most populated regions) poised for heightened challenges in reconciling water demand and availability. While increasing trends are found in precipitation, AET, and NWA for the northern region of Texas based on SSP2–4.5, decreasing trends are found over the southern region for all three parameters based on SSP5–8.5. These findings underscore the importance of factoring both spatial and temporal variations in water availability and demand for effective water management strategies and the need for adaptive water management strategies for the changing water availability scenarios.

Strengthening rural community water safety planning in Pacific Island countries: evidence and lessons from Solomon Islands, Vanuatu, and Fiji.

Pacific Island Countries (PICs) collectively have the lowest rates of access to safely managed or basic drinking water and sanitation globally. They are also the least urbanised, have dynamic socioeconomic and increasing climate-linked challenges. Community-based water managers need to respond to variability in water availability and quality caused by a range of hazards. Water Safety Planning (WSP), a widely adopted approach to assessing water supply, offers a risk-based approach to mitigating both existing and future hazards. WSP is adaptable, and making modifications to prescribed WSP to adapt it to the local context is common practice. Within the Pacific Community Water Management Plus research project, we used formative research and co-development processes to understand existing local modifications, whether further modifications are required, and, to develop additional modifications to WSP in Fiji, Vanuatu and Solomon Islands. The types of additional local modifications we recommend reflect the unique context of PICs, including adjusting for community management of water supplies and required collective action, community governance systems, levels of social cohesion in communities, and preferred adult-learning pedagogies. Incorporating modifications that address these factors into future WSP will improve the likelihood of sustained and safe community water services in Pacific and similar contexts.

Increased belowground tree carbon allocation in a mature mixed forest in a dry versus a wet year.

Tree species differ in their carbon (C) allocation strategies during environmental change. Disentangling species-specific strategies and contribution to the C balance of mixed forests requires observations at the individual tree level. We measured a complete set of C pools and fluxes at the tree level in five tree species, conifers and broadleaves, co-existing in a mature evergreen mixed Mediterranean forest. Our study period included a drought year followed by an above-average wet year, offering an opportunity to test the effect of water availability on tree C allocation. We found that in comparison to the wet year, C uptake was lower in the dry year, C use was the same, and allocation to belowground sinks was higher. Among the five major C sinks, respiration was the largest (ca. 60%), while root exudation (ca. 10%) and reproduction (ca. 2%) were those that increased the most in the dry year. Most trees relied on stored starch for maintaining a stable soluble sugars balance, but no significant differences were detected in aboveground storage between dry and wet years. The detailed tree-level analysis of nonstructural carbohydrates and δ13 C dynamics suggest interspecific differences in C allocation among fluxes and tissues, specifically in response to the varying water availability. Overall, our findings shed light on mixed forest physiological responses to drought, an increasing phenomenon under the ongoing climate change.

Comprehensive analysis of spatiotemporal variability of rainfall-based extremes and their implications on agriculture in the Upper Ganga Command Area.

The agricultural sector in India primarily relieson monsoon rains, making it necessary for agricultural water managers to study variations in water availability by analyzing rainfall patterns. This information is critical for deciding cropping patterns and irrigation approaches, managing water resources, and improving crop water productivity. The long-term spatiotemporal variability over the command area, India Meteorological Department (IMD) based selection of thresholds for extremes indices, and thorough analysis of the consequences of extreme on agriculture make the study unique. These aspects collectively enhance the perception of the climate-agriculture relationship, which is essential for promoting agriculture resilience under changing rainfall patterns. This type of research is very limited in the literature. Therefore, the present study focuses on comprehensively analyzing the spatiotemporal variability of rainfall and extreme precipitation indices and their implications on agriculture. The study is carried out in the UpperGanga Command Area (UGCA), India's oldest irrigation canal system, by using long-term (1901-2021) high-resolution (0.25 × 0.25°) daily rainfall gridded data obtained from IMD, Pune. Eight different extreme rainfall indices are used to assess spatiotemporal variations. The Mann-Whitney-Pettitt test identified 1970 as a significant change point. Rainfall trends and extreme indices for pre- and post-1970 periods were examined using the non-parametric modified Mann-Kendall test. The results show significant increases in rainfall trends for the annual, monsoon, and kharif seasons from 1901 to 1970, but significant decreases were observed during 1971-2021. This difference resulted in a noticeable decrease in average precipitation in the latter period, approximately 62mm less than in 1901-1970. Similarly, extreme precipitation indices, including the number of rainy days (NxRainy), consecutive dry days (CWD), simple daily intensity index (SDII), and total precipitation (PRCPTOT), exhibited increasing trends in 1901-1970, but they showed significant decreasing trends in 1971-2021. In addition, there is a strong positive correlation between these indices and total precipitation. The study also found that geographical factors influence these trends, with all indices, except SDII, strongly correlated with latitude and elevation, but not with longitude. The implications of these negative rainfall and extreme rainfall trends were further analyzed, and the results indicate a significant impact on the cropping patterns in the study area. The present research findings will be beneficial for regional water resource managers and policymakers in better understanding the existing trends in rainfall distribution over the UGCA.

Root transcriptomic provides insights on molecular mechanisms involved in the tolerance to water deficit in Pisum sativum inoculated with Pseudomonas sp.

Root transcriptomics and biochemical analyses in water-stressed Pisum sativum plants inoculated with Pseudomonas spp. suggested preservation of ABA-related pathway and ROS detoxification, resulting in an improved tolerance to stress. Drought already affects agriculture in large areas of the globe and, due to climate change, these areas are predicted to become increasingly unsuitable for agriculture. For several years, plant growth-promoting bacteria (PGPB) have been used to improve legume yields, but many aspects of this interaction are still unclear. To elucidate the mechanisms through which root-associated PGPB can promote plant growth in dry environments, we investigated the response of pea plants inoculated with a potentially beneficial Pseudomonas strain (PK6) and subjected to two different water regimes. Combined biometric, biochemical, and root RNA-seq analyses revealed that PK6 improved pea growth specifically under water deficit, as inoculated plants showed an increased biomass, larger leaves, and longer roots. Abscisic acid (ABA) and proline quantification, together with the transcriptome analysis, suggested that PK6-inoculated plant response to water deficit was more diversified compared to non-inoculated plants, involving alternative metabolic pathways for the detoxification of reactive oxygen species (ROS) and the preservation of the ABA stress signaling pathway. We suggest that the metabolic response of PK6-inoculated plants was more effective in their adaptation to water deprivation, leading to their improved biometric traits. Besides confirming the positive role that PGPB can have in the growth of a legume crop under adverse conditions, this study offers novel information on the mechanisms regulating plant-bacteria interaction under varying water availability. These mechanisms and the involved genes could be exploited in the future for the development of legume varieties, which can profitably grow in dry climates.

Water availability may not constrain vegetation growth in Northern Hemisphere

With global climate warming, the variability of climate and weather tends to increase driving the water resources available for vegetation become more uncertain. Therefore, there is still a debate as to how vegetation response to, and to which extent it is constrained to water availability. In this study, we analyzed the correlation between vegetation growth and water availability in the Northern Hemisphere from 1982 to 2018. The condition of vegetation growth was characterized by Normalized Difference Vegetation Index (NDVI) and Leaf Area Index (LAI), while the Standardized Precipitation Evapotranspiration Index (SPEI) represented water condition. Our results suggest that the water deficit stress on vegetation growth in the Northern Hemisphere caused by global warming may not be as severe as described in previous studies. Although there was an increasing trend in areas where vegetation growth was constrained by water deficit in the Northern Hemisphere, such trend was not significant; in contrast, there was a significant decreasing trend in areas where vegetation growth was constrained by surplus water. In addition, there was a spatial variability in water availability for vegetation growth at mid and high latitudes. We further found that the response time of vegetation to both water deficit and water surplus was increasing, indicating that the cumulative effect of water availability on vegetation growth was delaying, and that vegetation tends to be affected by climatic extreme events such as drought with longer time scales. Our results highlight the need to reconsider the response of vegetation activities to water availability, and shed light on a more divers reaction pattern of vegetation to water in the context of climate change.

Impact Assessment of Livestock Production on Water Scarcity in a Watershed in Southern Brazil

This study presents the assessment of water scarcity associated with livestock production in a watershed in Southern Brazil where 115 farms (poultry, pig, and milk) are located. The methods, AWARE—available water remaining, and BWSI—blue water scarcity index, were applied monthly for the year 2018, and the characterization factors (CF) were regionalized into five scenarios evaluated by varying water availability and environmental water requirements. Livestock water consumption accounted for 94.1% of the total water consumed. Low water scarcity was observed in all scenarios (BWSI < 0). The highest CFAWARE was observed in scenario 3, ranging from 2.15 to 9.70 m3 world eq.m3, with higher water scarcity in summer. In the same scenario, pig production presented the highest annual average water scarcity footprint (WSF) of 90.3 m3 world eq./t carcass weight. Among milk production systems, pasture-based systems presented the highest annual average WSF of 52.7 m3 world eq./t fat protein corrected milk, surpassing semi-confined and confined systems by 12.4% and 3.5%, respectively. In scenario 3, poultry production presented an annual average WSF of 49.3 m3 world eq./t carcass weight. This study contributes knowledge to the livestock sector to perform the assessment of water scarcity.

Functional traits patterns along an altitudinal gradient in a large tropical forest region

Understanding the link between functional traits and environmental gradients can provide important information to face global change. Here, we assessed how environmental variables act on functional trait-based ecological strategies of the acquisitive-conservative continuum and dispersal syndromes in forests of the Rio Doce Basin in Brazil's Atlantic Forest. Through literature and herbarium measurements, we gathered data on ten functional traits related to light interception, leaf economics spectrum, and reproductive ability from 1912 woody species across 79 localities. Relationships between community-weighted means of functional traits and an altitudinal gradient encompassing thermal and water availability variables were quantified using generalized linear models and principal component analysis. We found that in higher altitudes are predominant vegetative conservative functional strategies (smaller leaves and petioles) and reproductive acquisitive functional strategies (smaller fruits and seeds and abiotic dispersed species). The thermal variables mainly influenced vegetative functional traits, which showed a predominantly acquisitive strategy in warmer areas, where there are more favorable and stable conditions for rapid growth and resource uptake. The water variables had a pronounced impact on reproductive functional traits, particularly in terms of dispersal patterns. Water availability tends to impact the costs of fleshy fruits and seeds with higher energy content. The patterns found for the altitudinal gradient reflected a combination of thermal and water variables, which is congruent with the aggregative role of altitude, composed of multiple physical and climatic conditions. In conclusion, the abiotic factors are operating on a large landscape scale in the plant communities, exerting influence on functional traits along the altitudinal gradient in a tropical forest region.

The Sphagnum cuspidatum complex: phylogeny, species delimitation, and morphology

Abstract The use of species as a concept is an important metric for assessing biological diversity and ecosystem function. However, delimiting species based on morphological characters can be difficult, especially in aquatic plants that exhibit high levels of variation and overlap. The Sphagnum cuspidatum complex, which includes plants that dominate peatland hollows, provides an example of challenges in species delimitation. Microscopic characters that have been used to define taxa and the possibility that these characters may simply be phenoplastic responses to variation in water availability make species delimitation in this group especially difficult. In particular, the use of leaf shape and serration, which have been used to separate species in the complex, have resulted in divergent taxonomic treatments. Using a combination of high-resolution population genomic data (RADseq) and a robust morphological assessment of plants representing the focal species, we provide evidence to evaluate putative species in this complex. Our data support the recognition of S. cuspidatum, S. fitzgeraldii, S. mississippiense, and S. trinitense as genetically distinct species that can be separated morphologically. These results indicate that S. viride does not differ genetically from S. cuspidatum. Our results are broadly relevant to other aquatic groups where leaf shape and marginal teeth are used to distinguish species.

Hymenaea stignocarpa Mart. ex Hayne growth–climate relationships are regulated by soil water saturation in Cerrado-Pantanal ecotone

The expected intensification of the dry season, and concentration of rainfall during the wet season, can disrupt tree growth and regional biodiversity in the Cerrado-Pantanal transition zone. Thus, this study aims to assess the climatic responses of Hymenaea stigonocarpa tree growth, a common tree species in this region. Incremental cores were collected at breast height (ca. 1.3 m) from 67 trees to construct a dendrochronological series to correlate annual growth with local meteorological variables and large-scale atmospheric circulation indices from the Pacific and Atlantic Oceans. Significant positive correlations were observed between tree growth and the Pacific Ocean indices. Maximum and average air temperatures of the previous dry season negatively influenced growth, while precipitation at the beginning of the growth season (November) positively influenced growth. Tree growth was not correlated with temperature or rainfall during the wet season. However, at the end of the wet season (February), tree growth was negatively correlated with air temperature and positively correlated with rainfall, but the relationship shifted in the next month (March) suggesting that soil water saturation reduced growth. Our results indicate that dendrochronological studies of H. stignocarpa are useful for assessing the environmental change on the Cerrado-Pantanal ecotone. Furthermore, variations in water availability and temperature associated with changes in large-scale oceanic circulation and local meteorological conditions will impact the growth dynamics of this important Cerrado tree species.

Water use strategies of Nitraria tangutorum in the lake-basin region of the Badain Jaran Desert.

Information regarding plant water-use strategies is essential for understanding the hydrological processes and plant survival adaptation mechanisms in desert lake basin regions. To examine the water use strategies of plants in desert lake basin areas, water uptake patterns, water use efficiency, and water potential of Nitraria tangutorum were investigated at different distances from the lake duringhe growing seasons in the lake basin regions of the Badain Jaran Desert. The results indicate that N. tangutorum primarily absorbed groundwater in May (63.8%) and August (53.5%), relied on deep soil water in June (75.1%), and uniformly absorbed soil water from different layers in July. These observations could be explained by periodic fluctuations in the groundwater level and the consequent decrease in soil water availability, as well as plant root adjustments. As soil water availability decreases, N. tangutorum adapts to water variation by increasing its water use efficiency (WUE) and reducing its leaf water potential (Ψ). With intensified water stress, N. tangutorum gradually shifted from adventurous anisohydric regulation to conservative isohydric regulation. Thus, N. tangutorum responds to diverse degrees of environmental changes by altering its water-use strategy. A better understanding of the adaptive water use strategies developed by desert plants under varying water availability conditions provides insight into the diversity of species' reactions to long-term drought and quantifies the hydrological cycle of desert ecosystems against the background of worldwide climate warming.

Dynamics of crop category choices reveal strategies and tactics used by smallholder farmers in India to cope with unreliable water availability

CONTEXTChanging cropping pattern is a potentially effective lever to cope with unreliable water resources, but given the multiple factors driving crop choices, assessing if farmers actually use it specifically for this objective remains difficult. OBJECTIVEWe aimed at analyzing whether and how farmers choose crop categories with different water requirements to cope with limited water resources in peninsular India. METHODSWe monitored over a 10 year period crop choices, weather, and groundwater level for the three cropping seasons in 205 irrigable farms in the Berambadi watershed, in southern India. We categorized crops according to their seasonal water requirement. We built farm types based of Sequence Analysis and Agglomerative Hierarchical Clustering of crop category sequences over 10 years for each cropping season. For each type, we correlated the variation in crop category choices to variations in rainfall and groundwater availability, to identify tactical adaptations. Finally, we grouped the crop category choices of the three seasons to identify the main strategic pathways followed by farmers. RESULTS AND CONCLUSIONSSequence analysis of crop category choices revealed different types of crop category sequences, reflecting farmers' different strategies, which were not significantly linked with groundwater availability. We identified five main pathways across the three cropping seasons, including combining long-cycle irrigated crop and other crop categories, specializing in short-cycle irrigated crops over two or three seasons, specializing in rainfed crops or abandoning agriculture. Within each type, correlations between variation in water availability and crop categories highlighted specific tactical adaptations. SIGNIFICANCEThe opportunity for farmers to choose their crops among a variety of species encompassing a large range of water requirements allows them to base their system resilience on a large diversity of strategies and tactics. This suggests that some farmers empirically estimate the water balance of their cropping systems at seasonal scale to take tactical decisions. Providing them with science-based tools to refine this estimation could therefore improve their decision-making. This also implies that modelling farmer decisions must account for their diversity. Maintaining or increasing the capacity of farmers to cultivate a broad range of crops with different seasonal water requirements is important for farming system resilience, and should therefore be part of the agenda of policy makers for agricultural or environmental regulations.

Chasing the fitness optimum: temporal variation in the genetic and environmental expression of life-history traits for a perennial plant.

The ability of plants to track shifting fitness optima is crucial within the context of global change, where increasing environmental extremes may have dramatic consequences for life history, fitness, and ultimately population persistence. However, tracking changing conditions relies on the relationship between genetic and environmental variance, where selection may favour plasticity, the evolution of genetic differences, or both depending on the spatial and temporal scale of environmental heterogeneity. Over three years, we compared the genetic and environmental components of phenological and life-history variation in a common environment for the spring perennial Geum triflorum. Populations were sourced from alvar habitats that exhibit extreme but predictable annual flood-desiccation cycles and prairie habitats that exhibit similar but less predictable variation in water availability. Heritability was generally higher for early life-history (emergence probability) relative to later life-history traits (total seed mass), indicating that traits associated with establishment are under stronger genetic control relative to later life-history fitness expressions, where plasticity may play a larger role. This pattern was particularly notable in seeds sourced from environmentally extreme but predictable alvar habitats relative to less predictable prairie environments. Fitness landscapes based on seed source origin, largely characterized by varying water availability and flower production, described selection as the degree of maladaptation of seed source environment relative to the prairie common garden environment. Plants from alvar populations were consistently closer to the fitness optimum across all years. Annually, the breadth of the fitness optimum expanded primarily along a moisture gradient, with inclusion of more populations onto the expanding optimum. These results highlight the importance of temporally and spatially varying selection in life-history evolution, indicating plasticity may become a primary mechanism needed to track fitness for later life-history events within perennial systems.

Comparing actual transpiration fluxes as measured at leaf-scale and calculated by a physically based agro-hydrological model

The main purpose of this paper is to compare the actual transpiration rates from tomato crop, as measured at leaf scale and estimated by a macroscopic approach in an agro-hydrological model, named FLOWS-HAGES, under variable soil properties and water availability. To this aim, sixteen plots were cultivated with tomatoes in Metaponto, Southern Italy. Soil hydraulic properties (SHP) were obtained using a fast in-situ characterization method. Leaf-area index (LAI) was measured using a leaf-area meter. SHP and LAI were then used in the physically-based FLOWS-HAGES which allowed calculating the macroscopic transpiration rates, Ta,m. Single-leaf transpiration rates, Ta,l, and stomatal conductance, gs,l, were measured in situ. For comparing with Ta,m, gs,l was upscaled by Big-Leaf approach to canopy scale stomatal conductance, gs,c, which was applied to Penman-Monteith model to obtain the canopy-scale transpiration, Ta,c. Finally, multiple linear regression (MLR) was used to find the statistical relationship between Ta,m and Ta,c, and the SHP and gs,c. Results showed that the macroscopic approach smooths the spatial variability of transpiration rates. Ta,c increased with the saturated water content, θs, and the slope of the water retention curve, n, while Ta,m decreased with increasing θs and n. MLR improved significantly by introducing gs,c to predict Ta,m.

Human influence on water availability variations in the upper Ewaso Ng’iro river basin, Kenya

Study regionUpper Ewaso Ng’iro catchment is located in Eastern Africa – a water-scarce region. Study focusStreamflow is in decline in the catchment despite the pattern of increasing amounts of rainfall in the East African region. This study explored historical human-water interplays to understand the coevolution of hydrological systems and societal development and to identify the dominant features contributing to water deficits and water-related conflicts in the lowland zone of the catchment. A socio-hydrological conceptual framework was used to mimic and explain the two-way coupling between human and hydrological systems. New hydrological insights for the regionThe results show that the dominant features that have likely contributed to changes in lowland streamflow and water-related conflicts include: population growth, land use/cover changes, and economic dynamics. The dry season flows have been extremely reduced with a 100% reduction observed in the month of February especially between 2010 and 2020 while the wet season flows have increased by about 10% and 15% in the upland and midland zones respectively. The decreasing trends in the streamflow against increasing amounts of rainfall emphasize the direct role humans have on catchment water availability. East Africa being a water-scarce region, there is a need to shift the focus from ‘the sustainable natural flows perspective’ to ‘the amount of water retained during wet seasons perspective’, improving land conservation activities to increase water infiltration during wet seasons, and the need to bring all stakeholders together for collective understanding.

Spatiotemporal variation in water availability drives insect community dynamics in an urban riparian zone

Water bodies can mitigate urban heat island effects and allow terrestrial animals to access water during periods of insufficient precipitation. Because precipitation is expected to become increasingly scarce in many global regions, urban riparian areas in drylands may yield important insight into the dynamic role of water in terrestrial animal communities. Here, we first investigated the role of spatiotemporal variability in water availability in insect biomass and biodiversity in an urban riparian area—particularly, whether seasonality modulates the spatial effects of water availability. High water availability was characterized spatially by proximity to a river, and temporally by high-precipitation seasons. Second, we investigated whether the relationship between biomass and biodiversity shifts due to variation in water availability. We determined the biomass and biodiversity of an insect community across a riparian zone in Stockton, CA, USA, an urban drylands area characterized by hot, dry summers and cool, wet winters. Time (seasonality exhibiting dramatic variation in precipitation) exerted strong effects on ecological indices and a biodiversity-biomass relationship. Space (proximity to a fixed water source) had more modest effects on the community, and there was some evidence that space and time modulated the effects of one another on the community. Urban animal community dynamics may be more sensitive to larger-scale climate patterns than to local, landscape-level factors, and covariation between biomass and biodiversity may be influenced by resource (water) availability. Studying insect communities in the riparian zones of urban drylands may be critical to understanding how animal communities respond to a warmer, drier climate.