Role Of Water Availability Research Articles

Widespread potential for streamflow leakage across Brazil

River-aquifer interactions play a crucial role in water availability, influencing environmental flows and impacting climate dynamics. Where groundwater tables lie below river water levels, stream water can infiltrate into the underlying aquifer, reducing streamflow. However, the prevalence of these “losing” rivers remains poorly understood due to limited national-wide in situ observations. Here we analyze water levels in 17,972 wells across Brazil to show that most of them (55%) lie below nearby stream surfaces, implying that these nearby streams are likely seeping into the subsurface. Our results demonstrate the widespread potential for stream water losses into underlying aquifers in many regions of the country, especially in areas with extensive groundwater pumping. Our direct observations underscore the importance of conjunctively managing groundwater and surface water, and highlight the widespread risk of streamflow losses to aquifers, which could impact global water access and ecosystems that rely on rivers.

Response of Helenium amarum to Environmental Stressors in the Presence of Mycorrhizal Fungi and Its Role as a Pollinator Resource

Globally, climate change is causing shifts in precipitation patterns. Shifting precipitation patterns can be a stressor for many species. One species that is experiencing such stress is Helenium amarum Raf (H. Rock). H. amarum, thrives in dry upland pastures and low-lying grassy and sandy habitat in the mid-Atlantic (USA), where it persists despite storm-driven standing water. Helenium amarum is a species that is toxic to livestock and has been found outside its native range. Temperature and light impacts on germination are already known, but the role of water availability and potential ameliorating effects of mycorrhizae during water stress have not been studied. We planted seeds collected from nature in the Aquatics Facility at Old Dominion University under varied water regimes (drought, flood, intermediate) and evaluated supplemental mycorrhizal fungi impacts on plant traits. Plants in soil with supplemental mycorrhizae grew to nearly twice the height of ‘no supplement’ controls (x¯mycorrhizae = 23.16, S.D. = 7.33 cm; x¯control = 13.70, S.D. = 6.33 cm; p < 0.001). Leaf length was also greater with supplemental mycorrhizae ( x¯mycorrhizae = 3.52, S.D. = 1.27 cm; x¯control = 2.66, S.D. = 0.75 cm; p = 0.0239). Leaf number was greater in high water treatments, with supplemental mycorrhizae (high-water: x¯mycorrhizae = 27.47, S.D. = 10.66; x¯control = 13.50, S.D. = 6.80; p < 0.001; pulse-water x¯mycorrhizae = 30.50, S.D. = 8.64; x¯control = 22.38, S.D. = 7.42; p = 0.0254). This work demonstrates that H. amarum tolerates both dry and moist soil during germination, which may be relevant for successful invasiveness. Supplemental mycorrhizal fungi buffer the effects of water stress, which is significant as climate change impacts precipitation. Additionally, we have documented that pollinators frequently visit flowers of the plant, which is indicative that the species provides ecosystem services in the form of pollinator resources.

Soil fungal communities contribute to the positive diversity–productivity relationship of tree communities under contrasting water availability

Abstract Plant diversity has often been linked to increased productivity; however, this apparent diversity–productivity relationship may rely on intertrophic interactions such as those between plants and soil microbes. Soil fungi can create complementarity between plant species via altered plant resource partitioning, facilitation via fungal networks or biotic feedbacks, thereby promoting plant diversity–productivity relationships. Furthermore, these relationships are likely to be context dependent in response to resource availability. We used a biodiversity–ecosystem function experiment with trees exposed to high and low water availability treatments to determine the contribution of soil fungal communities to the diversity–productivity relationship in tree communities. We used amplicon sequencing of soil fungi to assess fungal richness, community composition and richness of functional guilds. We then applied structural equation modelling to determine relationships between tree diversity, fungal communities and tree productivity and the role of water availability in these relationships. Tree species richness and functional diversity both increased above‐ground tree productivity and influenced soil fungal community composition. Fungal community composition had a direct impact on tree productivity and enhanced net diversity effects on productivity. Therefore, fungal communities mediated a positive, indirect effect of tree richness on productivity. While total fungal richness was not associated with tree diversity, pathogen richness decreased and mycorrhizal richness increased with tree richness. Pathogen and mycorrhizal richness had either no impact or a weak negative effect on productivity. Tree species traits strongly affected fungal communities and these changes promoted productivity. Finally, water availability greatly influenced fungal communities but did not interact with tree diversity to affect productivity; indicating possible resilience of tree communities to altered precipitation regimes and associated changes in fungal communities. Synthesis: Our study highlights the crucial role that fungal communities play in shaping the relationship between tree diversity, traits and productivity, and resilience to altered water availability.

Glacier and climate evolution in the Pariacacá Mountains, Peru

Glaciers in Peru play a major role in water availability and they also have direct implications on natural hazards such as glacial lake outburst floods (GLOFs) and/or ice avalanches, which have caused a high number of fatalities and damage to infrastructure in the last decades. Despite a noticeable effort to quantify and understand the shrinking and thawing of glaciers in Peru, there are still regions where detailed assessment is still missing.In this work, a set of remote sensing images were used to map, for the first time, the evolution of the glaciated area (from 1970 to 2018) in the Pariacacá Mountains (11º5’ S, 76º0’ W) in the Cordillera Central of Peru. The results evidenced a marked decrease of the glaciated surface, with 55.3% shrinkage since 1970 and 40% since 1987. Faster glacier retreat occurred between 1985 and the end of the 1990s, and this period was followed by a significant slowdown in shrinking rates. The differential loss of ice, depending on elevation and exposure to incoming radiation, has led to changes in spatial distribution of the glaciers. Currently, they have almost completely thawed below 5000 m a.s.l. They are mostly located in south- to west-facing aspects. Ice melting in the last decades has even affected the summit areas. Finally, the development of ablation hollows has been identified as an important driver of glacier thaw. These features are formed mainly in gentle slopes and highly irradiated zones between 5000 and 5400 m a.s.l.

Reversed Surface-Mass-Balance Gradients on Himalayan Debris-Covered Glaciers Inferred from Remote Sensing

Meltwater from the glaciers in High Mountain Asia plays a critical role in water availability and food security in central and southern Asia. However, observations of glacier ablation and accumulation rates are limited in spatial and temporal scale due to the challenges that are associated with fieldwork at the remote, high-altitude settings of these glaciers. Here, using a remote-sensing-based mass-continuity approach, we compute regional-scale surface mass balance of glaciers in five key regions across High Mountain Asia. After accounting for the role of ice flow, we find distinctively different altitudinal surface-mass-balance gradients between heavily debris-covered and relatively debris-free areas. In the region surrounding Mount Everest, where debris coverage is the most extensive, our results show a reversed mean surface-mass-balance gradient of −0.21 ± 0.18 m w.e. a−1 (100 m)−1 on the low-elevation portions of glaciers, switching to a positive mean gradient of 1.21 ± 0.41 m w.e. a−1 (100 m)−1 above an average elevation of 5520 ± 50 m. Meanwhile, in West Nepal, where the debris coverage is minimal, we find a continuously positive mean gradient of 1.18 ± 0.40 m w.e. a−1 (100 m)−1. Equilibrium line altitude estimates, which are derived from our surface-mass-balance gradients, display a strong regional gradient, increasing from northwest (4490 ± 140 m) to southeast (5690 ± 130 m). Overall, our findings emphasise the importance of separating signals of surface mass balance and ice dynamics, in order to constrain better their contribution towards the ice thinning that is being observed across High Mountain Asia.

Glacier Changes between 1976 and 2015 in the Source Area of the Ayeyarwady (Irrawaddy) River, Myanmar

The Ayeyarwady River in Myanmar is one of the largest rivers in Southeast Asia. It is predominantly fed by monsoonal precipitation and, to a lower extent, by meltwater from glaciers located in the Himalaya mountains. Information about the glaciers in its headwater region and glacier changes is scarce. Glaciers, in general, are highly important for the hydrological system and are contributing to river flow, therefore playing a key role in water availability, especially in catchments with (semi-) arid downstream areas as is in parts of Myanmar. This study investigated 130 glaciers in the Ayeyarwady headwaters by analyzing satellite images from Landsat missions between 1976 and 2015. The results of the glacier area and volume change analyses indicate that the glaciers are experiencing unprecedented losses. Over the 39 years, the glaciers lost up to 54.3 ± 7.64% of their area and 60.09 ± 1.56% of their mass and volume. The highest losses occurred in the period 2002–2015, which corresponds to increasing global and local warming. This development will probably have a strong influence on the glaciers’ storage function and will affect the local river runoff in the headwater region.

Sensitivity of stomatal conductance to soil moisture: implications for tropospheric ozone

Abstract. Soil moisture and water stress play a pivotal role in regulating stomatal behaviour of plants; however, in the last decade, the role of water availability has often been neglected in atmospheric chemistry modelling studies as well as in integrated risk assessments, despite the fact that plants remove a large amount of atmospheric compounds from the lower troposphere through stomata. The main aim of this study is to evaluate, within the chemistry transport model CHIMERE, the effect of soil water limitation on stomatal conductance and assess the resulting changes in atmospheric chemistry testing various hypotheses of water uptake by plants in the rooting zone. Results highlight how dry deposition significantly declines when soil moisture is used to regulate the stomatal opening, mainly in the semi-arid environments: in particular, over Europe the amount of ozone removed by dry deposition in one year without considering any soil water limitation to stomatal conductance is about 8.5 TgO3, while using a dynamic layer that ensures that plants maximize the water uptake from soil, we found a reduction of about 10 % in the amount of ozone removed by dry deposition (∼ 7.7 TgO3). Although dry deposition occurs from the top of canopy to ground level, it affects the concentration of gases remaining in the lower atmosphere, with a significant impact on ozone concentration (up to 4 ppb) extending from the surface to the upper troposphere (up to 650 hPa). Our results shed light on the importance of improving the parameterizations of processes occurring at plant level (i.e. from the soil to the canopy) as they have significant implications for concentration of gases in the lower troposphere and resulting risk assessments for vegetation or human health.

Structure stabilization in starch-quinoa bran doughs: The role of water availability and gelatinization

Bran is a promising ingredient for nutritional fortification in starch-based dough systems. However its incorporation is a technological challenge favoring a shift in dough functionality. The objective of this study was to elucidate the impact of bran on baking performance independent of dough firmness and start of gelatinization. Therefore, corn starch was replaced by quinoa bran (10% to 50%) and water addition (80–110g/100g flour) was standardized on a fixed complex shear modulus (G*) and start of gelatinization (TOnset) based on a corn starch reference dough. A destabilizing effect by bran particles was counteracted in corn starch dough by adjusting the water content up to 110 g/100g flour. Moreover, a negative correlation between TOnset and loaf volume was determined (r=− 0.9042), thus an early TOnset should be aspired in order to prevent gas release and to stabilize corn starch- quinoa bran dough.

Impact of filamentous cyanobacteria on the water quality of two tropical reservoirs

ABSTRACT Artificial lakes play an important role in water availability in tropical semi-arid Northeastern Brazil. However, in addition to the negative effects that dams have on the water quality of rivers, other practices such as discharge of untreated wastewater, intensive crop fertilization and fish farming have been contributing to water quality deterioration. Climate change may be another driver of water quality decrease. Increases in precipitation and drought intensities as well as temperature increase may redefine the dynamics of planktonic communities and favour species more adapted to the new environment. Water samples were collected in two reservoirs selected based on the recurrence of positive results for saxitoxins, Acarape do Meio (AM) and Sitios Novos (SN). In general, diversity in SN (1.08) was higher than in the AM (0.60). Phytoplankton dynamics in these reservoirs differ from other reservoirs in the same region of Brazil, in the sense that filamentous cyanobacteria are dominant. Furthermore, lower diversity, concentration and richness of chlorophyceae and bacillariophyceae were found in both reservoirs. Increase in diversity was observed during the intense rainy season of 2011, suggesting a slight improvement of water quality. A close inverse correlation between Cylindrospermopsis sp and other cyanobacteria was found in SN (R2= –0.862) and in AM (R2= –0.997) and the data collected demonstrates that a season with intensive rainfall may lead to lower cyanobacteria concentrations probably due to water dilution and higher flushing rates.

Factors Affecting the Disease Severity of Alternaria Blackspot In Natural Brassica rapa Populations On the California and Oregon Coasts

Abstract Fungal disease has important effects in natural and agricultural plant populations; however, we are still uncovering factors that influence severity in these systems. Understanding these factors is especially important because it has been predicted that climate change will increase fungal disease widely as a result of changes in precipitation. Here, we investigate the role of water availability and other ecological variables in determining disease severity of a foliar fungal disease. For this study, we focused on natural populations of an important annual, herbaceous plant, Brassica rapa and its fungal disease, Alternaria blackspot. We explored three hypotheses: (1) The factors that drive disease severity differ early in the growing season compared to late in the growing season. (2) Disease severity patterns for this fungus are driven by water availability to a greater extent than other ecological variables. (3) Disease severity increases with plant density. To address these hypotheses, data were...

Regional sea-surface temperatures explain spatial and temporal variation of summer precipitation in the source region of the Yellow River

ABSTRACTThe summer precipitation (June–September) in the source region of the Yellow River accounts for about 70% of the annual total, playing an important role in water availability. This study divided the source region of the Yellow River into homogeneous zones based on precipitation variability using cluster analysis. Summer precipitation trends and teleconnections with global sea-surface temperatures (SST) and the Southern Oscillation Index (SOI) from 1961 to 2010 were investigated by Mann-Kendall test and Pearson product-moment correlation analysis. The results show that the northwest part (Zone 1) had a non-significantly increasing trend, and the middle and southeast parts (zones 2 and 3) that receive the most precipitation displayed a statistically significant decreasing trend for summer precipitation. The summer precipitation in the whole region showed statistically significant negative correlations with the central Pacific SST for 0–4 month lag and with the Southern Indian and Atlantic oceans SST for 5–8 month lag. Analyses of sub-regions reveal intricate and complex correlations with different SST areas that further explain the summer precipitation variability. The SOI had significant positive correlations, mainly for 0–2 months lag, with summer precipitation in the source region of the Yellow River. It is seen that El Niño Southern Oscillation (ENSO) events have an influence on summer precipitation, and the predominant negative correlations indicate that higher SST in equatorial Pacific areas corresponding to El Niño coincides with less summer precipitation in the source region of the Yellow River.Editor Z.W. Kundzewicz; Associate editor D. Gerten

Influence of Soil on Root Distribution: Implications for Quality of Tocai Friulano Berries and Wine

The Tocai Friulano cultivar grafted onto SO4 rootstock was studied for three years in four soil types (SU1 to SU4) in the Colli Orientali del Friuli AOC, Italy. The grapevine root system, soil chemical and physical properties, soil water regime, vine performance, and grape and wine quality were studied with the aim of better understanding how roots mediate the vine response to different soil characteristics. Climate was homogeneous in the study area, and the effect of weather was evaluated on an annual basis. Our results showed that soil played a major role in water availability to the vine and affected vine yield components, vegetative growth, vine balance, grape composition, and wine sensory profile. Observation of roots provided information about variability in vine performance and wine characteristics. Good, stable wine quality was obtained only in soils that allowed development of a deep root system (SU1 and SU4); these soils produced satisfactory wine quality even in dry seasons. In dry years, an imbalance between vegetative and reproductive growth occurred in shallow soils, in which the root systems were thin and superficial (SU2), and led to poor-quality grapes and wines. Conversely, the wines showed more interesting characteristics when the root systems were more dense and distributed throughout the soil profile (SU3). These results underline the importance of analyzing root characteristics when evaluating the vine response to the soil–climate environment.

Efficiency of Contracts for Differences (CfDs) in the Nordic Electricity Market

This paper presents new and updated evidence on the efficiency of the EPAD contracts in the Nordic financial electricity market, based on a long sample of 14 years, from 2000 to 2013 inclusive. The Electricity Price Area Differentials (EPADs) are used to hedge against price differences between a bidding area and the Nordic system price. The aim of this paper is twofold. First, we estimate the magnitude and significance of ex-post risk premia in EPAD products (season, month, quarter, year) with delivery in 2000-2013. Further, we estimate the relationship between spot and futures prices by vector autoregression (VAR) model. By observing Granger causalities, adjustments to price shocks, and decomposing variance, we aim to shed light on the EPADs’ efficiency. Second, we elaborate on some determinants of risk premia and test the roles of time-to-maturity and open interest on risk premia. We additionally consider, for the Nordic system an essential energy source, the role of water availability in the hydro reservoirs on explaining local area price spreads. We support and reject some of the earlier findings about the limited efficiency of the EPADs and bring new empirical evidence on the drivers behind the regional price dynamics.

The nocturnal water cycle in an open‐canopy forest

The movement of moisture into, out‐of, and within forest ecosystems is modulated by feedbacks that stem from processes which couple plants, soil, and the atmosphere. While an understanding of these processes has been gleaned from Eddy Covariance techniques, the reliability of the method suffers at night because of weak turbulence. During the summer of 2011, continuous profiles of the isotopic composition (i.e., δ18O and δD) of water vapor and periodic measurements of soil, leaf, and precipitation pools were measured in an open‐canopy ponderosa pine forest in central Colorado to study within‐canopy nocturnal water cycling. The isotopic composition of the nocturnal water vapor varies significantly based on the relative contributions of the three major hydrological processes acting on the forest: dewfall, exchange of moisture between leaf waters and canopy vapor, and periodic mixing between the canopy and background air. Dewfall proved to be surprisingly common (∼30% of the nights) and detectable on both the surface and within the canopy through the isotopic measurements. While surface dew could be observed using leaf wetness and soil moisture sensors, dew in the foliage was only measurable through isotopic analysis of the vapor and often occurred even when no dew accumulated on the surface. Nocturnal moisture cycling plays a critical role in water availability in forest ecosystems through foliar absorption and transpiration, and assessing these dynamics, as done here, is necessary for fully characterizing the hydrological controls on terrestrial productivity.

The role of water availability on weed–crop interactions in processing tomato for southern Italy

Anthropogenic climate change is projected to increase the occurrence of drought for the Mediterranean region. The aim of this study was to quantify the role of increasing drought on weed-induced crop losses and crop–weed interactions for processing tomato grown in southern Italy. Field experiments were carried out during 2008 and 2009. Two levels of water availability were imposed to compare weed competitive effects under irrigated and rainfed conditions on tomato as a means to quantify weed–crop interactions and associated crop losses when water is limited. In this study, the absolute decline in tomato yields by weed interference was a direct function of water applied (rain + irrigation); however, the relative effect of weed biomass on crop loss appeared to increase under drought when compared to irrigated conditions. Overall, these data indicate that the relative decline in tomato fresh weight from weeds was actually greater under drought, and that the relative crop losses (per unit of weed biomass) actually declined as water availability increased. From a management standpoint, these data suggest that if drought occurrences do increase in the Mediterranean region with climate change, there may be a greater need for complete and thorough weed control for this production system.

Influence of shifting flow paths on nitrogen concentrations during monsoon floods, San Pedro River, Arizona

Hydrologic flow paths control transport, and therefore are a major constraint on the cycling and availability of nutrients within stream ecosystems. This control is particularly evident in semiarid streams, where hydrologic connectivity between stream, riparian, and upland systems increases greatly during storms in the rainy season. We measured chloride concentrations in base flow, precipitation, soil water, and stream water to quantify the hydrologic connectivity and solute flux between soil water, groundwater, and the stream channel during six summer floods in 2001 (a wet year; 25 cm winter rain) and 2002 (a dry year; 5 cm winter rain) in the San Pedro River, southeastern Arizona. This hydrologic information was used to evaluate observed patterns in nitrate, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations in floods. The first floods of each year showed increased stream nitrate concentration that was approximately two orders of magnitude higher than base flow concentration. DOC consistently doubled to tripled during storm events, while DON in 2001 showed no response and showed a marked increase in 2002. A chloride mixing model indicated that soil and groundwater contributions to storm water discharge were related to antecedent conditions and to flood magnitude. Soil and groundwater contributions were the highest early in the 2001 monsoon season following the wet winter, much lower early in 2002 following a dry winter, and lowest during the largest floods of the 2002 monsoon season when flows were derived primarily from precipitation and overland flow. Stream water nitrate‐N concentrations during floods were consistently 0.2–0.5 mg/L higher in 2002 than during 2001, suggesting greater over‐winter accumulation of soil nitrate during the drier year. This result is consistent with higher mean nitrate‐N concentrations in soil water of the riparian zone in 2002 (3.1 mg/L) than in 2001 (0.56 mg/L). These data highlight the importance of seasonal and interannual variability of hydrology in semiarid regions, and the role of water availability in driving patterns of soil nutrient accumulation and their transport to the stream.

Strong site effects dictate nutrient patterns in a Mediterranean floodplain

Nutrient patterns in wetlands are usually studied at a single sampling station and not for more than two or three hydrological years. This makes environmental assessment difficult, particularly when spatial heterogeneity and wetland responses depend upon water availability, as often occurs in Mediterranean wetlands. Furthermore, the spatial scale of environmental control of wetland dynamics is usually hypothesized to change as a result of water connectedness, so the higher the rate of water renewal, the larger the spatial scale of environmental control. To test this idea, we carried out a study of monthly nutrient loadings, organic carbon, total nitrogen, and phosphorus in a Spanish hypertrophic floodplain (Tablas de Daimiel National Park) for six years at three sites to ascertain the significance of both the spatial heterogeneity and the long-term responses of nutrient patterns to water availability. Our study demonstrated that strong site effects prevailed on nutrient chemistry in this wetland, irrespective of the degree of wetland connectivity, since there were very few significant correlations among different sites for a single nutrient and no significant correlations with loadings. Causes for this behavior might be that water inputs to this Mediterranean wetland were highly variable and leveling ecological effects were dampened by site processes. Spatially, an increasing gradient of total organic carbon and nitrogen occurred toward the outlet, but total phosphorus peaked in the middle of the wetland. Such a decoupling was also shown by PCA analysis where three different factors explained 69% of overall variability of nutrient patterns: flooding, both organic carbon and total nitrogen content, and total phosphorus. No temporal trend in nutrient content was observed. No simultaneous seasonal patterns were obvious in nutrient data from the same site or for the same nutrient at different sites. Periodicity analyses did not show overlapping of annual rhythms. That lack of patterns could be evidence of the major importance of site processes. This wetland behaved as a sink for nutrients, a fact also suggested by the increasing carbon and phosphorus content in sediments of all sites over time. Sediment nitrogen dynamics, however, might experience differential among-site processes resulting in no trend in accumulation in some areas. These results challenge current views on the spatial scale of environmental control on wetland performance and suggest that the role of water availability in ecological connectivity may be more complex than previously suspected.

The role of water availability in seasonal growth of Bazzania trilobata on boulders in an eastern hemlock stand

Abstract Bryophyte growth is most often cited as being primarily water-limited; however, experimental manipulation of water availability in the field has not previously been employed to test this hypothesis. Here we follow the growth responses of a leafy liverwort, Bazzania trilobata, to field water addition treatments. Our study system was an eastern hemlock stand located in the lower Hubbard Brook Valley in northern New Hampshire where Bazzania forms pure colonies over boulders. The experimental design accounted for effects of boulder treatment (control, water addition or water plus nitrogen), aspect (north- or south-facing), position (top, east or west side of a boulder) and liverwort stem density. To follow growth responses of Bazzania, we tracked changes in biomass gain, stem elongation and branching over 86 days. Environmental measurements for the evaluation period and supplemental physiological data for Bazzania were also taken. An increase in water availability did not evoke a straightforward incr...

The Human Right to Water: Market Allocations and Subsistence in a World of Scarcity

This article presents an undergraduate student research project on water scarcity and basic rights to water by concentrating on multinational corporate ownership of water resources and the WTO´s trade-related role in water availability in Geneva, Switzerland.

Response Of Coastal Bermudagrass And Pensacola Bahiagrass To Applied Nitrogen And Seasonal Rainfall#

Applied nutrients and seasonal rainfall are both important inputs for forage production. A mathematical model is needed to link these factors. Since the logistic model provides a quantitative description of seasonal dry matter response to applied nutrients, the role of water availability should be identified. Previous analysis showed that the linear parameter A of the logistic model can incorporate this factor. In this article the relationship of A to seasonal rainfall, W, is shown to follow an exponential equation for Coastal bermudagrass (Cynodon dactylon L.) and Pensacola bahiagrass (Paspalum notatum Flügge). This agrees with previous results for corn (Zea mays L.). #Florida Agricultural Experiment Station Journal Series No. R-08720.