Patterns Of Water Availability Research Articles

Inter-model agreement on projected shifts in California hydroclimate characteristics critical to water management

Shifts away from the historical hydroclimate in populated regions can have dire consequences for water management. Regions like the state of California—where highly engineered, geographically interconnected, and inflexible water management systems are predicated on particular spatiotemporal patterns of water availability—are particularly vulnerable to hydroclimate shifts. However, much of the analysis of hydroclimate sensitivity to anthropogenic climate change has focused on gross metrics like annual mean precipitation, which is highly uncertain at the regional scale. This perceived uncertainty has deterred adaptation investments and quantitative integration of climate projection data into regional water management. Here, we assess projected future shifts in the state of California in a range of hydroclimate metrics critical to water management, using data from 10 statistically downscaled global climate model and two emissions scenarios currently used by the state. We find substantial inter-model agreement under both emissions scenarios—and > 80% inter-model agreement under the more severe climate change scenario—across metrics that collectively point toward an increasingly volatile, temporally concentrated, and extreme precipitation future for the state. We show, via hydrologic and operations modeling, that accounting for shifts in these more nuanced metrics reduces the projected reliability and sustainability of current water management practices to a greater degree than would be inferred from changes in total annual precipitation alone. These results highlight both the viability and critical importance of incorporating climate change projections quantitatively into water management decisions in California and other regions vulnerable to hydroclimate shifts, and underscore the need to develop integrated climate-hydrologic-operations models and decision-making protocols capable of accounting for all projected hydroclimate shifts.

Climate and phylogenetic history structure morphological and architectural trait variation among fine-root orders.

Fine roots mediate below-ground resource acquisition, yet understanding of how fine-root functional traits vary along environmental gradients, within branching orders and across phylogenetic scales remains limited. Morphological and architectural fine-root traits were measured on individual root orders of 20 oak species (genus Quercus) from divergent climates of origin that were harvested after three growing seasons in a glasshouse. These were then compared with similar measurements obtained from a phylogenetically diverse dataset of woody species from the Fine-Root Ecology Database (FRED). For the oaks, only precipitation seasonality and growing season moisture availability were correlated to aspects of root diameter and branching. Strong correlations among root diameters and architecture of different branch orders were common, while correlations between diameter and length were weakly negative. By contrast, the FRED dataset showed strong positive correlations between diameter and length and fewer correlations between root diameter and architectural traits. Our findings suggest that seasonal patterns of water availability are more important drivers of root adaptation in oaks than annual averages in precipitation and temperature. Furthermore, contrasting patterns of trait relationships between the oak and FRED datasets suggest that branching patterns are differentially constrained at narrow vs broad phylogenetic scales.

Climatic Fluctuations in Dry Steppes and Their Role in the Demutation Process

The water availability in dry steppes during various active growing seasons is analyzed for the first time. Climatic fluctuations are examined, and their specific features are determined. Contrary to the popular opinion that the maximum precipitation in the steppe zone occurs during the summer period and that this is a distinctive feature of the steppe zone that is applicable to all its subzones, analysis of dry steppes in the Lower Volga Region over a period of 64 years shows that the maximum precipitation is attributed to summer only in 39% of the studied years, to spring in 27% of the years, and to fall in the remaining 34% of the years. Analysis of the water availability time series produced for various seasons covering more than a semicentennial period shows a general trend: the summer precipitation is decreasing, while the precipitation in spring and fall is increasing. The application of the exponential smoothing method to the time series and regression analysis indicate a growth dynamics of water availability in the spring period after the watershed years of 1989 and 1990 (the data validity is confirmed by the Student’s t-test; the probability value is 0.0005) amid a decrease in the fall precipitation (the probability value is 0.01). These trends characterize the demutation processes ongoing in the secondary fallow phytocoenoses, which are manifested by the predomination of loose- and firm-bunch grasses: water availability in late spring (May) and early summer (June) plays a critical role in the generative process of these plants. In total, 28 species belonging to the Poaceae family have been identified in the studied phytocoenoses; their share in the total species richness is 24.5%. The water availability patterns indicate aridization of the climate in dry steppes. The presence of ephemeral and ephemeroid plants in the communities additionally confirms this: the spring precipitation is their key life support factor. The ephemeral and ephemeroid species constitute 8% of the total species richness.

Climate change will affect global water availability through compounding changes in seasonal precipitation and evaporation

Both seasonal and annual mean precipitation and evaporation influence patterns of water availability impacting society and ecosystems. Existing global climate studies rarely consider such patterns from non-parametric statistical standpoint. Here, we employ a non-parametric analysis framework to analyze seasonal hydroclimatic regimes by classifying global land regions into nine regimes using late 20th century precipitation means and seasonality. These regimes are used to assess implications for water availability due to concomitant changes in mean and seasonal precipitation and evaporation changes using CMIP5 model future climate projections. Out of 9 regimes, 4 show increased precipitation variation, while 5 show decreased evaporation variation coupled with increasing mean precipitation and evaporation. Increases in projected seasonal precipitation variation in already highly variable precipitation regimes gives rise to a pattern of “seasonally variable regimes becoming more variable”. Regimes with low seasonality in precipitation, instead, experience increased wet season precipitation.

Hydrological Characterization of Watering Ponds in Rangeland Farms in the Southwest Iberian Peninsula

Watering ponds are an important source of drinking water supply for livestock in semi-arid rangelands. Understanding the hydrological functioning of this kind of infrastructures is crucial for efficient water management in areas where water resources are often scarce. In this line, we have analyzed temporal patterns of water availability in a set of watering ponds located in Iberian rangelands and their relationship with temporal rainfall variability. In addition, the effectiveness of the ponds for conserving stored water during dry periods and some influencing factors (pond size and catchment area) have also been assessed. The results showed a high correlation between water availability and precedent rainfall, confirming, on the one hand, the capacity of storage of these infrastructures and, on the other hand, the importance of temporal rainfall patterns in their hydrological behavior. Our findings point to a minimum pond area of 2000 m2 and a catchment area/storage capacity ratio around 100 m−1 in order for watering ponds can face the dry summer period with certain guarantees, at least in regular hydrological years. Nonetheless, the vulnerability shown by the majority of the watering ponds in times of drought limits their usefulness as unique sources of water supply in many farms.

Optimization of Water Distribution to Support the Balance of Water Usage: A Case Study of the Sempor Irrigation System, Central Java, Indonesia

The existence of irrigation in Indonesia is commonly quite influenced by environmental and social cultural characteristics, which the people have lived by and developed for a long time. Many factors cause changes in the pattern of water availability, which increases competition among stakeholders, as in the Sempor irrigation system area. It has four main dams, which are the Bojong Dam, Watubarut Dam, Rowokawuk Dam, and Sindut Dam; it provides approximately 5900 ha of services and receives supplies from the Great Sempor Dam (38 million m3). Currently there is a decline in the function of this dam due to sedimentation, making operational services less optimal, especially during the dry season. The methodology of this study is to perform water optimization for the balancing of water in the irrigation area. Meanwhile, the implementation of the water supply on the field considers the calculation of water availability, space, and time. In practice, the operation of water supply is held by a group system in the secondary blocks. In certain conditions, the water rotation in tertiary channels was performed by local cultural wisdom.

Tapir population patterns under the disappearance of free-standing water

Baird’s tapir is the largest Neotropical tapir species, and it is considered Endangered by the IUCN. The Calakmul Biosphere Reserve (CBR) is the largest protected tropical forest in Mexico. The CBR is at the heart of the Maya Forest, a tri-national forest located in Mexico, Guatemala, and Belize that is the largest tropical forest outside the Amazon River basin. Free-standing water in the CBR occurs in only a few ephemeral ponds. These ponds are rare in the landscape, with a mean density of one pond in every 10 km2, and with an average distance among ponds of 3 km. Only some of these ponds have free-standing water in every year. A decreasing trend in water availability from these ponds was detected from 2008 to 2018. Our present objective was to document population of the tapirs during these 11 years, and reveal any relationship to the pattern of water availability. Using the technique of photo-trapping, we monitored from 9 to 15 ponds over a period of 8 years (a total of more than 18,000 camera-days) during the 11-year period. Results showed that although the population remained relatively stable, the index of relative abundance indicated a slight decrease in population abundance and in some sites seemed at least superficially associated with decreasing water availability. Such long-term population studies are becoming more important for estimating the impacts of possible changes and for predicting the future of populations. In turn, they assist the conservation of endangered and sensitive species such as Baird’s tapir.

Structural memory in grapevines: Early season water availability affects late season drought stress severity

Abstract In the future drought events are expected to occur more frequently, with unpredictable rain and heat events. In current research we investigated how different water availability patterns influenced late season plant water status in Vitis vinifera. ‘Cabernet Sauvignon’ grapevines were grown for three consecutive years. We compared the response to five water availability regimes: High, Intermediate, Low (along all season) and High-to-Low (High during the beginning of vegetative seasons switched to low during the rest of season) and Low-to-High (opposite treatment). Midday stem water potential (SWP) was measured weekly to determine the seasonal pattern of drought stress. Xylem anatomy was investigated by trunk vessel diameter measurements, and specific axial xylem conductivity was calculated according to Hagen-Poiseuille's law. Vines exposed to high water availability treatment showed improved seasonal water status along the season, compared to vines in the low treatment. Vines exposed to High-to-Low water regime showed a markedly improved water status at the beginning of the season, but became the most severely stressed toward the end of season. The SWP values were more negative in the High-to-Low regime even when compared to the Low water regime. Water availability at the beginning of the season (during main period of cambial activity) determined the vessel characteristics: high water availability during cambial activity increased vessel diameter and thus specific hydraulic conductivity. Our data strongly indicates that regulated drought stress can be induced by manipulating xylem structural parameters via controlling water availability during the period of stem cambial activity.

Spatial distribution of precipitation extremes over Rajasthan using CORDEX data

ABSTRACT Rainfall is one of the key climatic variables that affect the spatial and temporal patterns of water availability. One of the challenges posed by climate change is identification and quantification of extreme precipitation events. This study aims to analyse the extreme precipitation events for historical (1971–2000), near-future (NF) (2021–2050) and far-future (FF) (2070–2099) over Rajasthan. Non-parametric tests (Mann–Kendall [MK] test, modified MK and Sen’s slope estimator) are used for trend analysis. The precipitation extreme indices R50, R25, R99p and R95p were used to calculate the extreme events based on historical and future outputs of regional climate models (RCMs) REMO 2009 (driving global climate model [GCM] ‘MPI-ESM-LR’) and RegCM4 (driving GCM ‘CCCma-CanESM2’) from Coordinated Regional Downscaling Experiment (CORDEX). The performances of both RCMs were evaluated against observed (Indian Meteorological Department [IMD]) daily precipitation data. The observed historical (IMD) data show that R99p threshold values are slightly overestimated by REMO 2009 and underestimated by RegCM4. The indices R25 and R95p simulated by REMO 2009 show a significant decreasing trend in FF of RCP8.5 scenario. Overall REMO 2009 performed better in simulating the key features of the spatial distribution of R95p (R99p) threshold and annual average frequency of R25 (R50) in historical period as compared to RegCM4. Abbreviations: NF: Near-future; FF: Far-future; MK: Mann-Kendall; RCM: Regional climate model; GCM: Global climate model; EPT: Extreme precipitation threshold; IMD: Indian Meteorological Department; CORDEX: Coordinated Regional Climate Downscaling Experiment

Urban Water Crises under Future Uncertainties: The Case of Institutional and Infrastructure Complexity in Khon Kaen, Thailand

This paper uses the emerging crises in water management in North East Thailand as a case study to examine the effectiveness of existing institutional structures and processes to adapt to an uncertain future climate. We argue that it is through an analysis of the interface of actors, institutions and physical infrastructure that climate vulnerability can be better understood, and conversely, that climate resilience might be strengthened. This research has global significance as case studies of emerging water crises provide valuable insights into future vulnerabilities and the Thailand experience speaks to similar challenges across the global South. Our findings illustrate that water managers on the front line of dealing with climate variability are constrained by the interaction of infrastructure that was designed for different times and needs, and of institutional structures and processes that have emerged through the interplay of often competing organisational remits and agendas. Water management is further constrained by the ways in which information and knowledge are generated, shared, and then applied. Critically the research finds that there is no explicit consideration of climate change, but rather universally-held assumptions that patterns of water availability will continue as they have in the past. As a result, there is no long-term planning that could be termed adaptive, but rather, a responsive approach that moves from crisis to crisis between seasons and across years.

Stomatal Conductance Responses of Acacia caven to Seasonal Patterns of Water Availability at Different Soil Depths in a Mediterranean Savanna

Soil water availability controls plant productivity in seasonally dry ecosystems, although plant water use at different soil depths and times is, to the best of our knowledge, not clearly understood. Environmental variables at the canopy level and the soil volumetric water content (VWC) at five different soil depths were continuously recorded for three years (2011–2014) in an Acacia caven savanna site in central Chile. Stomatal conductance ( g s ) was measured every hour during daytime for 42 days distributed across the study period. Values of g s were weakly controlled by photosynthetically active radiation, vapor pressure deficit, and leaf temperature when considering the whole series. The variance proportion being explained increased from 5% to 20% if the whole series was partitioned into a dry and a wet season. According to the above, A. caven exhibited a more anisohydric behavior than previously thought. When we added the VWC in the root zone, to the g s atmospheric variables model, R2 increased to 47% when separately considering the dry and wet seasons. However, we did not find a differentiated use of water in the root zone, but instead a joint activity of the radicular system within the top 100 cm of the soil controlling g s .

Trends in extreme rainfall over ecologically sensitive Western Ghats and coastal regions of Karnataka: an observational assessment

Rainfall is one of the pivotal climatic variables, which influence spatio-temporal patterns of water availability. In this study, we have attempted to understand the interannual long-term trend analysis of the daily rainfall events of ≥ 2.5 mm and rainfall events of extreme threshold, over the Western Ghats and coastal region of Karnataka. High spatial resolution (0.25° × 0.25°) daily gridded rainfall data set of Indian Meteorological Department was used for this study. Thirty-eight grid points in the study area was selected to analyze the daily precipitation for 113 years (1901–2013). Grid points were divided into two zones: low land (exposed to the sea and low elevated area/coastal region) and high land (interior from the sea and high elevated area/Western Ghats). The indices were selected from the list of climate change indices recommended by ETCCDI and are based on annual rainfall total (RR), yearly 1-day maximum rainfall, consecutive wet days (≥ 2.5 mm), Simple Daily Intensity Index (SDII), annual frequency of very heavy rainfall (≥ 100 mm), frequency of very heavy rainfall (≥ 65–100 mm), moderate rainfall (≥ 2.5–65 mm), frequency of medium rainfall (≥ 40–65 mm), and frequency of low rainfall (≥ 20–40 mm). Mann-Kendall test was applied to the nine rainfall indices, and Theil-Sen estimator perceived the nature and the magnitude of slope in rainfall indices. The results show contrasting trends in the extreme rainfall indices in low land and high land regions. The changes in daily rainfall events in the low land region primarily indicate statistically significant positive trends in the annual total rainfall, yearly 1-day maximum rainfall, SDII, frequency of very heavy rainfall, and heavy rainfall as well as medium rainfall events. Furthermore, the overall annual rainfall strongly correlated with all the rainfall indices in both regions, especially with indices that represent heavy rainfall events which is responsible for the total increase of rainfall.

When the same is not the same: phenotypic variation reveals different plant ecological strategies within species occurring in distinct Neotropical savanna habitats

Variations in abiotic characteristics such as soil water availability and fertility impose different selective pressures on plant populations. This may produce intraspecific variability in functional traits, even at a fine spatial scale. We investigated whether functional traits related to water-use efficiency, resource-retention strategy, soil nutrient acquisition, and fire tolerance differ in species that occur in two different habitats of Brazilian Cerrado: rocky savannas and savanna woodlands. Rocky savannas occur over sandstone, quartzite outcrops and have shallow nutrient-poor and low-moisture rocky soils, while savanna woodlands occur over well-drained and deep soils with frequent fire regimes. We measured nine functional traits of 40 tree species that occur in both habitats. Rocky savanna individuals exhibited a greater water-use efficiency strategy. The resource-retention strategy in rocky savanna individuals was corroborated by lower adult maximum height. However, despite the lower nutrient availability in rocky savanna soils, we only detected lower leaf phosphorus content in individuals from this habitat. Furthermore, individuals from both habitats had equally thick bark, suggesting that the fire-defense strategy is related to a stable, rather than plastic trait. Overall, our results highlight the central role of contrasting soil water availability patterns in driving phenotypic plasticity within species. We conclude that savanna species are responding to water and nutrient availabilities, via plasticity in traits related to the resource-retention strategy, and preparing for future fires, via uniformly thick bark. Wide plant distribution in contrasting habitats is possible for species that can shift ecological strategies to survive in nutrient- and water-limited habitats such as rocky savannas.

Managing diversions in unregulated streams using a modified percent‐of‐flow approach

Abstract In Mediterranean‐type river systems, naturally low seasonal stream flows are often overexploited, which has implications for managing flows for environmental as well as human needs. Traditional approaches to instream flow management are not well suited to unregulated systems with strong seasonal patterns of water availability and many water diverters, and are challenging to implement in such systems. They often do not protect the full range of variability in the annual hydrograph, require extensive site‐specific data, expensive modelling or both. In contrast, holistic flow management strategies, such as percent‐of‐flow (POF) strategies are designed to protect multiple ecological processes and preserve inter‐annual flow variability. However, POF approaches typically require real‐time streamflow gauging, and often lack a robust metric relating a diversion rate to ecological processes in the stream. To address these challenges, we present a modified percent‐of‐flow (MPOF) diversion approach where diversions are allocated from a streamflow baseline which is derived from a regional relationship between a conservative streamflow‐exceedance and date. The streamflow baseline remains the same from year to year, and is independent of water‐year type. This approach protects inter‐annual flow variability and provides a predictable daily allowable volume of diversion at any diversion point—supporting efficient water management planning. The allowable diversion rate in the MPOF approach is based not on a fixed percentage of the ambient streamflow, but rather on a maximum allowable percentage change in riffle crest thalweg depth, an ecologically meaningful, common hydraulic measurement. In this paper, we demonstrate that the MPOF approach is a holistic approach well suited to manage diversions in unregulated streams typical of California's Mediterranean‐type coastal drainages.

Soil control over the distribution of Mediterranean oak forests in the Montsec mountains (northeastern Spain)

Models of plant species distribution and response to global change rely mostly on climatic variables alone, whereas soil variables are usually not taken into account. Evergreen and marcescent oaks are therefore considered to share environmental niches in the Mediterranean region despite their functional differences. We studied the distribution of forests dominated by either Quercus ilex (QI plots) or Q. faginea/Q. subpyrenaica (QF plots) in 46 plots at an altitude between 570m and 980m on a north-facing slope in northeastern Spain. We used binomial logistic regression and classification tree analysis to explain the distribution of the two types of forest. Soils of the sample plots were mostly Lithic Xerorthents developed from limestone. Surface mineral horizons of QI forests had higher organic carbon (C), nitrogen (N), and NaOH-extractable phosphorus concentrations, while organic layers had smaller values of the C/N and C/P ratios. Soils of QF forests accumulated higher amounts of C despite the lower concentration in their surface mineral horizons. The distribution of QF and QI forests was significantly explained by the variability in soil available water-holding capacity and rock fragment content, QF forests appearing on soils with over 22mm of available water-holding capacity and <26% rock fragments. The presence of Acer monspessulanum, a secondary tree species, was related to soils with few rock fragments and high pH. Soil variability produces different patterns of water availability under homogenous macroclimatic conditions that are differently suited to the two types of forest. Information about whole soil profiles is required in the assessment of present vegetation distribution and future response to climate change.

Field investigations of the 2013–14 drought through quali-quantitative freshwater monitoring at the headwaters of the Cantareira System, Brazil

ABSTRACTIntegrating seasonal patterns of water availability and land-use/land-cover change is crucial in watershed planning. Often, these are not considered under hydrological extremes affecting decision making. This article presents results from a multi-site, nested catchment experiment carried out during a dry period in the Cantareira Water Supply System, South-East Brazil, linking quali-quantitative freshwater monitoring to land-use/land-cover change. Results from 17 catchments show regional behaviour for nitrate loads and drainage areas (0.66–925 km2). An inverse correlation between forest cover and water yield was observed. Despite forest growth in spatial extent, nutrient loads showed potential hazards for water security.

A comparison of Cladocera and Copepoda as indicators of hydroperiod length in Mediterranean ponds

Yearly variation in water availability patterns has a remarkable effect in the presence of freshwater microcrustacean species. We hypothesize that, based on their different reproductive strategies, Cladocera and Copepoda may show differences in their association with ponds of different hydroperiods, i.e. in their indicator value. In order to test our hypothesis, cladoceran and copepod assemblages from ponds in Mediterranean woodlands in Latium (Italy) were analysed to evaluate their role as indicators of ponds attributed to four hydroperiod categories. Twenty-five cladocerans and sixteen copepods were collected. Correspondence analysis performed on the copepod species matrix clearly arranged the sites along a hydroperiod gradient; conversely, the same analysis carried out on cladocerans failed to distinguish between the hydroperiod categories. An indicator species analysis confirmed that copepods have a higher fidelity to the target site group. The high ability of copepods in discriminating ponds with different wet phase durations suggests their use as indicators of hydroperiod variation due to land use and climate change.

High-resolution isotope measurements resolve rapid ecohydrological dynamics at the soil-plant interface.

Plants rely primarily on rainfall infiltrating their root zones - a supply that is inherently variable, and fluctuations are predicted to increase on most of the Earth's surface. Yet, interrelationships between water availability and plant use on short timescales are difficult to quantify and remain poorly understood. To overcome previous methodological limitations, we coupled high-resolution in situ observations of stable isotopes in soil and transpiration water. We applied the approach along with Bayesian mixing modeling to track the fate of (2) H-labeled rain pulses following drought through soil and plants of deciduous tree ecosystems. We resolve how rainwater infiltrates the root zones in a nonequilibrium process and show that tree species differ in their ability to quickly acquire the newly available source. Sessile oak (Quercus petraea) adjusted root uptake to vertical water availability patterns under drought, but readjustment toward the rewetted topsoil was delayed. By contrast, European beech (Fagus sylvatica) readily utilized water from all soil depths independent of water depletion, enabling faster uptake of rainwater. Our results demonstrate that species-specific plasticity and responses to water supply fluctuations on short timescales can now be identified and must be considered to predict vegetation functional dynamics and water cycling under current and future climatic conditions.

Effects of an Invasive Grass (Phalaris Arundinacea) on Water Availability in Semi-Arid Riparian Zones

In much of the western United States, riparian zones are shifting from native woody and herbaceous species to invasive grasses, potentially altering plant water use and availability. Compared to the woody species they often replace, dense grass stands may have higher productivity and transpiration, causing them to use more water. We investigated evidence of this effect in semiarid eastern Washington, where many streams experience low flow that degrades water quality and habitat. Most of these riparian zones have extensive stands of invasive reed canary grass (Phalaris arundinacea), which could reduce stream flow through high transpiration rates. We tested how growing season, transpiration, and specific leaf area of reed canary grass compared to native riparian plant species to assess its effects on plant water use and water availability. Reed canary grass had a longer growing season by two weeks compared to eight other common riparian species. Although its transpiration rates per leaf area are not exceptional, its high specific leaf area and ability to produce dense stands of biomass resulted in more photosynthetic surface through which to transpire water than any other species tested, and substantially higher estimates of transpiration per ground surface area. We present strong evidence that reed canary grass is altering the patterns of water availability and use in these systems.

Heterogeneous flows foster heterogeneous assemblages: relationships between functional diversity and hydrological heterogeneity in riparian plant communities

Summary Riparian ecosystems are biophysically complex and highly diverse taxonomically, structurally and functionally. While many environmental factors determine the structure and function of riparian vegetation communities, hydrology is thought to be the ‘master variable’. Flooding and variability in water availability are known to be key drivers of taxonomic diversity, but their influence on the functional trait diversity of riparian vegetation communities remains largely unexplored. We collected data on species abundance, quantitative plant functional traits and hydrology from 15 sites distributed across south‐eastern Australia to address the following questions: (a) Is functional trait diversity related to the frequency and magnitude of flooding disturbance? (b) Is functional trait diversity related to variability in seasonal water availability within the riparian zone? We confirm that metrics describing both flooding disturbance and patterns of water availability exhibit strong relationships with functional trait diversity in riparian vegetation communities of south‐eastern Australia. Our key finding is that functional trait diversity in these systems tends to be positively associated with variability in hydrological conditions and the intensity of rare, high‐magnitude flooding events, rather than average patterns of flow. Our study highlights the importance of extreme flooding events and temporal patterns of water availability as determinants of diversity in riparian vegetation communities. These relationships may have significant consequences for plant communities experiencing alterations to hydrology caused by anthropogenic flow modification and the changing climate.