Water Mass Balance Research Articles

What roles do architectural design and on-site water servicing technologies play in the water performance of residential infill?

More than half of new urban residential developments are planned as infill in Australia's major cities. This provides an unprecedented opportunity to use innovative design and technology to address urban water challenges such as flooding, reduced water security and related infrastructure and urban heat island issues. However, infill can have positive or negative water impacts, depending on architectural design and on-site water servicing technologies implemented. In this study we asked, “What influence does residential infill development have on the local urban water cycle?” and “What roles do architectural design and technologies play?” To answer these questions, a set of 196 design-technology configurations were developed by combining 28 architectural designs and 7 on-site water-servicing technology options. The configurations represent three cases: (i) existing (EX) or before infill, (ii) business-as-usual development (BAU), and (iii) alternative development (ALT). Using the Site-scale Urban Water Mass Balance Assessment (SUWMBA) model and a set of water performance indicators, the impact of configurations on the urban water cycle was quantified. The results showed BAU, on average, increases population density, stormwater discharge, and imported water by 98%, 44% and 85%, and decreases evapotranspiration and infiltration by 53% and 34%, compared to the EX conditions. More population density (141%) with lower impacts on the urban water cycle (21% and 64% increase for stormwater discharge and imported water, and 29% and 17% reduction in evapotranspiration and infiltration) can be achieved by appropriate integration of ALT designs and technologies. Architectural design has a greater influence on urban water flows than the implementation of on-site water servicing technologies. The results have a great implication for sustainable urban water management for managing the risks associated with pluvial flooding, water insecurity, and urban heat. It also highlights the underutilised role of architects and urban planners to address urban water issues.

Modeling temporal changes in salinity and fluoride concentration of Lake Ulungur in Xinjiang, China

为研究乌伦古湖矿化度和氟化物浓度与各水量因子间的定量关系，本研究以水量平衡和物质平衡为基础，把影响湖水水质的原因分为降雨、蒸发、河流补给、地下水补给以及地下水流出5个水量因子，定量分析湖水矿化度和氟化物浓度与各水量因子之间的关系，并且预测了湖水矿化度和氟化物浓度的动态变化.结果表明，地下水输出流量决定了湖水中矿化度和氟化物浓度，地下水输出流量越大，湖水中的矿化度和氟化物浓度越小.2010年至今乌伦古湖水位的升高导致了地下水输出流量增大，乌伦古湖内的矿化度和氟化物浓度均呈缓慢下降趋势，模型预测新的稳态下湖水中矿化度为1.68 g/L，氟化物浓度为1.70 mg/L，在地下水输出流量不变的情况下达到新的稳态所需时间大约为50 a.;In order to evaluate the quantitative relationship between salinity and fluoride concentration and their control factors in Lake Ulungur in Xinjiang, China, this study develops a model for predicting stable state and dynamic water salinity based on water mass balance and solute balance. The input parameters are rainfall, evaporation, river recharge, groundwater recharge, groundwater outflow, and their associated salinity. The concentration of fluoride can also be modeled following the same approach, which provides another constraint on input parameters. The results show that the groundwater outflow significantly affects the salinity and fluoride concentration in lake water, with increasing outflow leading to lower salinity and fluoride concentration in Lake Ulungur. The rise of lake water level leads to increased outflow of groundwater in Lake Ulungur between 2010 and 2020, and the salinity and fluoride concentration in lake water decreased slowly. Our model predicts that the salinity of the Lake Ulungur in the new stable state is 1.68 g/L, and the concentration of fluoride is 1.70 mg/L, but it will take roughly 50 years to reach the new stable state given that the outflow rate remains constant.

A hybrid approach for integrated surface and subsurface hydrologic simulation of baseflow with Iterative Ensemble Smoother

Integrated surface and subsurface hydrologic models are particularly well suited for the simulation of baseflow as exchange fluxes does not rely on boundary conditions. Regional scale hydrologic models are of particular interest as they can provide guidance to stakeholders toward sustainable water resources management. However, integrated hydrologic models are rarely considered at the regional scale because their computational costs usually prevent efficient model calibration and predictive uncertainty analysis. Moreover, estimation of baseflow and each water budget component usually requires additional post-processing steps. In this paper, we thus aim here to provide a hybrid approach for the application of an integrated hydrologic model at the regional scale when low-flow processes are of primary concern. A surface water mass balance module has been developed to solve the hydrological mass balance from precipitations and temperature datasets. This module calculates potential infiltration fluxes that are used as input to the integrated modeling platform HydroGeoSphere (HGS). This approach provides a computationally tractable integrated model where low-flow processes are explicitly considered, baseflows generated in an integrated fashion, and each water budget component accessible. The model is applied to a region covering 36 900 km2 in the Southeastern part of the province of Quebec, Canada. Thanks to the computational efficiency of the approach, a rigorous mathematical parameter estimation, the Levenberg–Marquardt form of the Iterative Ensemble Smoother, can be considered to calibrate the model to baseflow of eight main rivers, snow water equivalent and evapotranspiration. An ensemble of 187 equally-probable realizations was used for history matching of observations and for the non-linear uncertainty analysis. An improved representation of baseflow can be linked to an appropriate non-linear uncertainty quantification through an efficient integrated surface and subsurface hydrologic model to support managing water resources at the regional scale.

Assessing water circularity in cities: Methodological framework with a case study

With significant efforts made to consider water reuse in cities, a robust and replicable framework is needed to quantify the degree of urban water circularity and its impacts from a systems perspective. A quantitative urban water circularity framework can benchmark the progress and compare the impacts of water circularity policies across cities. In that pursuit, we bring together concepts of resource circularity and material flow analysis (MFA) to develop a demand- and discharge-driven water circularity assessment framework for cities. The framework integrates anthropogenic water flow data based on the water demand in an urban system and treated wastewater discharge for primary water demand substitution. Leveraging the water mass balance, we apply the framework in evaluating the state of water circularity in Singapore from 2015 to 2019. Overall, water circularity has been steadily increasing, with 24.9% of total water demand fulfilled by secondary flows in 2019, potentially reaching 39.6% at maximum water recycling capacity. Finally, we discuss the wider implications of water circularity assessments for energy, the environment, and urban water infrastructure and policy. Overall, this study provides a quantitative tool to assess the scale of water circularity within engineered urban water infrastructure and its application to develop macro-level water systems planning and policy insights.

Fate of phosphorus from treated wastewater in soil-based constructed wetlands

In France, soil-based constructed wetlands for the discharge of treated wastewater have become a popular technique to both reduce flow to surface receiving water bodies and perform complementary treatments. This study focuses on the fate of phosphorus in three different soils, as well as its assimilation by Phragmites australis. The experimental set-up consisted of three lysimeters containing three soils selected to be representative of those typically found near wastewater treatment plants (i.e. a silt loam Fluvisol, a sandy loam Fluvisol and a sandy-clay loam Technosol). Lysimeters are undisturbed soil monoliths (1.5 m3 in volume), whose masses are continuously monitored in order to obtain an accurate water mass balance. The lysimeters here were intermittently fed for 3.5 days and then left to rest for 3.5 days. The experiment lasted 26 months, including 18 months of feeding with phosphorus (PO4-P, TP) fluxes in and out being monitored along with water content, oxygen content and redox potential at various depths. The quantities of phosphorus stored in the soils and assimilated in the Phragmites australis were measured. Phosphorus fractionation in soils was performed to better understand its distribution and potential remobilization. Low phosphate concentrations were measured at the outlets of all three lysimeters, thereby highlighting satisfactory phosphorus retention in the three soils (removal efficiencies >90%). A significant amount of phosphorus can be exported by harvesting Phragmites australis aerial parts (26%, 17% and 13% of the yearly incoming phosphorus mass for the silt loam Fluvisol, sandy loam Fluvisol and sandy-clay loam Technosol, respectively). The fractionation step served to determine that the phosphorus retained in the soil was primarily bound to iron oxides/hydroxides, calcium and clay. Moreover, it was found to be preferable to hold oxidizing (aerobic) conditions and pH close to neutral in order to maintain conditions under which the complexes formed with phosphorus remain stable.

The Interannual Fluctuations in Mass Changes and Hydrological Elasticity on the Tibetan Plateau from Geodetic Measurements

The mass balance of water storage on the Tibetan Plateau (TP) is a complex dynamic system that has responded to recent global warming due to the special regional characteristics and geographical environment on the TP. In this study, we present global positioning system (GPS), gravity recovery and climate experiment (GRACE) and follow-on (FO) observations obtained during the 2002–2020 period to identify hydrological changes on the TP. The spatial long-term trends in the GRACE/GRACE-FO data show continuous glacier mass losses around the Himalayas and accumulated mass on the inner TP due to the increased water mass in lakes. The singular spectrum analysis (SSA) was applied for interpolation of the data gap with GRACE/GRACE-FO. We evaluated the correlation between the vertical displacements obtained from 214 continuous GPS stations and GRACE/GRACE-FO-modeled water mass loads and found a high correlation, with spatial variabilities associated with the seasonal terrestrial water storage (TWS) pattern. The common-mode component obtained from continuous GPS coordinates was decomposed using principal component analysis (PCA) and presented different periodic signals related to interannual fluctuations in hydrology and the dynamics of the inner Earth. Moreover, the various characteristics of precipitation and temperature revealed similar interannual fluctuations to those of the El Niño/Southern Oscillation. We conclude that the GPS-inferred interannual fluctuations and the corresponding GRACE/GRACE-FO-modeled hydrological loads reflect climate responses. These findings shed light on the complex role of the spatiotemporal climate and water mass balance on the TP since the beginning of the 21st century.

Quantification of the water age and submarine groundwater discharge in a typical semi-enclosed bay using stable oxygen (18O) and radioactive radium (228Ra) isotopes

Nutrient inputs from submarine groundwater discharge (SGD) play a significant role in sustaining primary productivity and nutrient cycling in the coastal area. Currently, various geochemical isotopes are used to trace the SGD processes. However, mass balance models of stable water isotopes (δ2H and δ18O) are seldom used in SGD estimating. In this study, mass balance models of 18O and radium (228Ra) isotopes were used to quantify the water age and SGD in Laizhou Bay, China based on the isotope data sampled in August 2017. The estimated age of water masses in Laizhou Bay ranged from 23.5 to 50.0 days with an average of 32.1 ± 16.3 days. The average SGD flux was (2.07 ± 1.04) × 108 m3 d−1, which was an order of magnitude larger than the Yellow River discharge during the sampling period. The sensitivity analysis revealed that estimated results of the water age and SGD are sensitive to the δ18O value in evaporation, as well as δ18O and 228Ra values in groundwater end-members. Based on the isotope method, the proportion of the Yellow River discharging into Laizhou Bay was estimated to be less than 27% of the total discharge. Furthermore, based on water and salt mass balance models, the estimated submarine fresh groundwater discharge (SFGD) flux ranged from (0.54–1.31) × 107 m3 d−1 with an average of (0.93 ± 0.46) × 107 m3 d−1. The SFGD accounted for 4.5% of the total SGD. Nutrient fluxes from SGD were significantly greater than those from the Yellow River, and SGD may have important effects on the marine ecosystem environments. This study reveals that stable and radium isotopes can be effectively combined to calculate the water age and SGD, which may be applied to the coastal area elsewhere.

When and Where do Free Bars in Estuaries and Tidal Channels Form?

AbstractThe incipient formation of free bars in weakly converging tidal channels and estuaries is mathematically framed within a unified two‐dimensional shallow water and sediment mass balance model. The analysis is driven by the recognition that none of the theoretical models introduced so far account for the spatially varying character of the planform morphology, which characterizes estuaries and creeks forming networks in coastal wetlands and in the tide‐dominated reaches of deltas. The problem is tackled by means of a linear stability analysis, by observing that width variations act on a spatial scale that is typically much longer than bars wavelength, allowing for an analytical treatment of the governing system of equations. We focus on two limit cases: first, the river transition into a micro‐tidal sea (estuarine case); second, a tidal channel in the absence of a fluvial supply of freshwater and sediment (coastal case). In the estuarine case, bars arise as a result of an intrinsic instability of the equilibrium state. Width increases toward the mouth leading to channel shallowing, which in turn promotes the development of multiple bars. This effect is partially counteracted by the channel deepening produced by the tidal action, which tends to reduce bar growth and migration rate. In the coastal case, tidal bars form far from the equilibrium state of the system, adapting instantaneously to the evolving bed profile, which in turn affects channel flow conditions. Noteworthy, the model suggests that the spatial‐temporal distribution of bars observed in nature reflects the evolutionary history of the system.

Analysis of the interannual variability in satellite gravity solutions: detection of climate modes fingerprints in water mass displacements across continents and oceans

This study analyzes the interannual variability of the water mass transport measured by satellite gravity missions in regard to eight major climate modes known to influence the Earth’s climate from regional to global scales. Using sparsity promoting techniques (i.e., LASSO), we automatically select the most relevant predictors of the climate variability among the eight candidates considered. The El Niño–Southern Oscillation, Southern Annular Mode and Arctic Oscillation are shown to account for a large part the interannual variability of the water mass transport observed in extratropical ocean basins (up to 40%) and shallow seas (up to 70%). A combination of three Pacific and one Atlantic modes is needed to account for most (up to 60%) of the interannual variability of the terrestrial water storage observed in the North Amazon, Parana and Zambezi basins. With our technique, the impact of climate modes on water mass changes can be tracked across distinct water reservoirs (oceans, continents and ice-covered regions) and we show that a combination of climate modes is necessary to explain at best the natural variability in water mass transport. The climate modes predictions based on LASSO inversions can be used to reduce the inter-annual variability in satellite gravity measurements and detect processes unrelated with the natural variability of climate but with similar spatio-temporal signatures. However, significant residuals in the satellite gravity measurements remain unexplained at inter-annual time scales and more complex models solving the water mass balance should be employed to better predict the variability of water mass distributions.

Cultivation of non-irrigated spring wheat in temperate free-grazing steppe improved both ecosystem and canopy water use efficiency

The temperate steppe in northern China is important for sandstorm control and food/livestock production. Understanding the influence and regulatory control of cultivation on the water balance and water use efficiency (WUE) of this water-limited region would promote the sustainability of local ecosystem and food supply. This study combined eddy covariance system observational data and the Shuttleworth–Wallace model to investigate evapotranspiration (ET) and its composition in paired sites, including a free-grazing steppe site and an adjacent site reclaimed for spring wheat cultivation in Xilinhot, Inner Mongolia. Further, analysis of the WUE of both the ecosystem (WUEE) and the canopy (WUEC) under the two sites showed that the mean daily gross primary productivity (GPP) of the cultivation site was 3.84 gC·m−2·d−1, i.e., 15.7% higher than that of the free-grazing site (3.32 gC·m−2·d−1). Compared with the free-grazing site (1.76 kgH2O·m−2·d−1), the mean daily ET of the cultivation site (1.40 kgH2O·m−2·d−1) was reduced by 20.7%. The difference in ET was due mainly to suppression of evaporation at the cultivation site from increased shading associated with a higher leaf area index (LAI). The largely increased GPP of the cultivation site fundamentally contributed to the 54.7% higher WUEC (4.75 gC·kg−1H2O) in comparison with the free-grazing site (3.08 gC·kg−1H2O). The WUEE of the cultivation site was 57.9% higher than that of the free-grazing site. The variation of transpiration of the free-grazing site explained 64% of the change of WUEC. These results indicate that land use differences in the temperate steppe area changed vegetation productivity substantially. Moreover, ecosystem ET and its composition, as well as large-scale land use change, might influence the regional water use pattern and mass balance. Our findings help clarify the impact of typical land use change on regional WUE, and could promote development of visionary and effective strategies for the use of the limited resources in arid–semiarid regions.

Using geochemistry to identify and quantify the sources, distribution, and fluxes of baseflow to an intermittent river impacted by climate change: The upper Wimmera River, southeast Australia

Documenting the distribution, sources and fluxes of baseflow discharge into rivers is important for their management and for maintaining ecosystem health. This study uses major ion geochemistry, 222Rn, and 3H to differentiate between the input of low-salinity near-river waters (bank storage and return waters and/or interflow) and regional groundwater in an intermittent river from southeast Australia that is undergoing long-term changes in flow resulting from climate change. Baseflow discharge calculated by 222Rn mass balance was up to 1.3 m3/m/day in the high flow period in July 2019 and up to 0.1 m3/m/day at low flow conditions in November 2019. The distribution of 222Rn activities implies higher baseflow fluxes in the upper and middle reaches that have relatively steep topography and higher hydraulic gradients. The lower reaches received less baseflow due to subdued topography and fine-grained sediments. The observation that Cl concentrations did not increase uniformly downstream, however, implies that much of the baseflow may comprise bank return flow or interflow. This conclusion is also consistent with water mass balance calculations and the observation that 3H activities (1.85–3.00 TU) in the river were higher than in the groundwater (<0.45 TU). Intermittent streams are likely to be less well connected to regional groundwater, and thus near-river water stores will be more important in sustaining streamflow during dry periods than regional groundwater. These rivers and their ecosystems may be less susceptible to the impacts of groundwater extraction and the near-river waters will provide a buffer zone from potentially contaminated regional groundwater. However, these near river stores are vulnerable to short-term climate variability, and changes to flow regimes resulting from climate change may significantly impact water supplies and ecosystem health.

Drying of foods under intermittent supply of microwave energy: proposal for a mathematical model

Intermittent microwave drying improves the quality of the dehydrated product, because reduces the effect of microwave hot spots. Mathematical modelling is essential to understand the physics of this drying process and to optimize the operation conditions. However, there are few modelling studies about intermittent microwave drying. This work proposed a mathematical model based on mass balances of liquid and vapor water in which a non-equilibrium formulation described the water phase change. The microwave heating, described by Lambert’s law, was accounting as source term on the thermal energy conservation equation. The numerical solution used the finite element method, and the experimental drying of potato samples validated the simulated drying. The values of moisture content and temperature obtained by numerical solution of the model showed good agreement with experimental data. From this, it was observed the presence of three periods in the drying kinetics: an initial heating phase almost without drying, follow by a phase with constant drying rate, and final a decrease of drying rate and temperature increasement. The model results showed that the interior temperature was higher than the surface temperature of sample, and there was water evaporation inside the potato. In additional, the gradients of temperature were reduced due to intermittency of the microwave power. This redistribution of temperature could contribute to the improvement of product quality during drying.

Regional Energy and Water Budget of a Precipitating Atmosphere over Ocean

AbstractEffects of water mass imbalance and hydrometeor transport on the enthalpy flux and water phase on diabatic heating rate in computing the regional energy and water budget of the atmosphere over ocean are investigated. Equations of energy and water budget of the atmospheric column that explicitly consider the velocity of liquid and ice cloud particles, and rain and snow are formulated by separating water variables from dry air. Differences of energy budget equations formulated in this study from those used in earlier studies are that 1) diabatic heating rate depends on water phase, 2) diabatic heating due to net condensation of nonprecipitating hydrometeors is included, and 3) hydrometeors can be advected with a different velocity from the dry-air velocity. Convergence of water vapor associated with phase change and horizontal transport of hydrometeors is to increase diabatic heating in the atmospheric column where hydrometeors are formed and exported and to reduce energy where hydrometeors are imported and evaporated. The process can improve the regional energy and water mass balance when energy data products are integrated. Effects of enthalpy transport associated with water mass transport through the surface are cooling to the atmosphere and warming to the ocean when the enthalpy is averaged over the global ocean. There is no net effect to the atmosphere and ocean columns combined. While precipitation phase changes the regional diabatic heating rate up to 15 W m−2, the dependence of the global mean value on the temperature threshold of melting snow to form rain is less than 1 W m−2.

Geophysical Challenges for Future Satellite Gravity Missions: Assessing the Impact of MOCASS Mission

The GRACE/GRACE-FO satellites have observed large scale mass changes, contributing to the mass budget calculation of the hydro-and cryosphere. The scale of the observable mass changes must be in the order of 300 km or bigger to be resolved. Smaller scale glaciers and hydrologic basins significantly contribute to the closure of the water mass balance, but are not detected with the present spatial resolution of the satellite. The challenge of future satellite gravity missions is to fill this gap, providing higher temporal and spatial resolution. We assess the impact of a geodetic satellite mission carrying on board a cold atom interferometric gradiometer (MOCASS: Mass Observation with Cold Atom Sensors in Space) on the resolution of simulated geophysical phenomena, considering mass changes in the hydrosphere and cryosphere. Moreover, we consider mass redistributions due to seamounts and tectonic movements, belonging to the solid earth processes. The MOCASS type satellite is able to recover 50% smaller deglaciation rates over a mountain range as the High Mountains of Asia compared to GRACE, and to detect the mass of 60% of the cumulative number of glaciers, an improvement respect to GRACE which detects less than 20% in the same area. For seamounts a significantly smaller mass eruption could be detected with respect to GRACE, reaching a level of mass detection of a submarine basalt eruption of 1.6 109 m3. This mass corresponds to the eruption of Mount Saint Helens. The simulations demonstrate that a MOCASS type mission would significantly improve the resolution of mass changes respect to existing geodetic satellite missions.

Optimal hydropower generation of Maithon multi‐purpose reservoir system

AbstractThe present study focuses on optimizing the hydropower generation capacity of a multi‐purpose reservoir system considering various constraints, including reservoir water mass balance, minimization of sediment, maximum and minimum reservoir water storage, maximum and minimum reservoir water releases, reservoir water drawdown levels, reservoir overflows, maximum flood zone space, and maximum and minimum storage constraints under 50%, 70% and 90% dependable inflow conditions The focus is the Maithon multi‐purpose reservoir system located at Maithon, a distance of 40.2 km from Dhanbad, the coal capital of India, in the State of Jharkhand. The study results indicate the derived policy is capable of producing maximum annual hydropower of 146,519.48 MWh/year for a 50% dependable inflow condition, 105,512.02 MWh/year for a 70% dependable inflow condition and 58,924.38 MWh/year for a 90% dependable inflow condition, compared to the existing hydropower generation of 129,428.4 MWh/year (average of last 10 years). A trade‐off between reservoir release water releases, mostly for meeting irrigation water needs and maximizing energy generation, was determined for use by various stakeholders and managers of reservoir operations.

Shallow landslide triggering in unsaturated vegetated slopes: Efficient computation of susceptibility maps

A modelling platform is developed to study the coupled hydromechanical processes occurring in shallow unsaturated slopes prone to landslide hazards. It is supplemented with a Graphical User-Interface (GUI) and relies on a finite element solver here referred to as cLiNUs (Computational Landslide Initiation through Numerical Simulations), which discretizes and solves the partial differential equations governing momentum and water mass balance for stratified deposits. cLiNUs allows the versatile simulation of hydrologic processes causing infiltration, surface runoff, moisture increase, deformation, and failure in shallow slopes. In addition, it is coupled with a novel vectorization strategy that enables the mapping of model computations on digital elevation models (DEM) to generate landslide susceptibility maps throughout the duration of storm events. The GUI includes routines for simple parameter initialization, selection of hydro-mechanical constitutive laws, determination of boundary conditions, and results’ visualization. The program also enables a straightforward use of data about stratigraphy (i.e., multiple soil layers within a slope profile), vegetation cover, swelling/shrinkage response of unsaturated soil deposits and water runoff, thus ensuring a variety of analyses for educational and scientific purposes. The capabilities of the new computational platform are illustrated with reference to multiple examples showcasing its ability for landslide susceptibility assessment at the scale of individual slopes. Furthermore, selected examples of regional scale performance are discussed, including spatiotemporal predictions of landslide triggering for a well-documented series of debris flows and runoff simulations taking into account the role of vegetation. The proposed framework opens new possibilities in landslide hazard zonation studies by enabling the incorporation of important datasets that otherwise would remain neglected (i.e., vegetation/land cover and its role on surface/subsurface flow, deformability/hydraulic properties of soil deposits, complex layering sequences of stratified slopes, transient rainfall, among others) while at the same time, relying on a user-friendly interface.

Water footprint and consumption of hydropower from basin-constrained water mass balance

Water management by the impoundment of reservoirs has been found to influence evapotranspiration not only locally but also at the basin scale. Highly regulated hydrological basins generally show the effect of a net increase in evapotranspiration accompanying the successive impoundment of reservoirs. However, understanding and isolating the effect from a particular single impounded reservoir remains a challenge due to the lack of long-term observation data required and the existence of many other drivers present at the basin scale. Focusing on the hydrological basin having the largest hydropower potential in China, we isolated in time and space and quantified the effects of a single impounded reservoir on evapotranspiration and the evaporative ratio (i.e., the ratio of actual evapotranspiration to precipitation) before and after the construction of the Ertan Dam in 1998. We find that the dam has increased evapotranspiration in the smallest subbasin by 46±15 mm/yr and the evaporative ratio by 0.05±0.015, from the period before impoundment (1983-1997) to that after impoundment (2000-2012). This increase is found only within the smallest differential subbasin holding the impounded reservoir and cannot be explained by other changes in land use or vegetation. We use this result from our hydrological basin-constrained approach to calculate the water footprint of the hydroelectric project as 16.5 m3/GJ, which accounts for additional hydroclimatic effects of the impoundment of the reservoir beyond the water surface. Hence, this study finds that when runoff data is available, the water consumption and the water footprint of hydropower projects can be calculated by water mass balance at the scale of their hydrological basins.

Creating a Water Quality Scale Methodology Using California as a Case Study

AbstractWater availability analysis traditionally has involved understanding how much water enters and leaves a region and how much is used or stored each year. This mass balance of water, or water...

Effect of multilayered groundwater mounds on water dynamics beneath a recharge basin: Numerical simulation and assessment of surface injection

AbstractInteractions between groundwater mounds caused by a geologic layer contrast affect the efficiency of managed aquifer recharge in arid areas. However, research has rarely examined the roles of groundwater mounding size variations on soil water dynamics in a stratified vadose zone in response to a sustained infiltration source. Numerical experiments were conducted on a two‐dimensional vertical‐section domain using HYDRUS software to simulate the behaviours of two adjacent (upper and lower) groundwater mounds underlying an infiltration basin subjected to clay loam and sandy alternately‐layered soil profiles. The model successfully predicted the volume and extent of perched water and approximated vertical travel times during events generating downward fluxes from the surface injection. The response time of the mounding width (lateral extension) to the surface injection was delayed as compared to that of the mounding height (vertical extension), especially for the lower water mound. The mounding heights and widths show a strongly positive correlation with the infiltration rates of both high‐ and low‐permeability layers where the injected water mounded, while the water storage amounts in the high‐ and low‐permeability layers were governed by the mounding height and width, respectively. Exploratory simulations were then employed to assess the dependence of groundwater mounding behaviours and recharge performances on surface injection strategies. Results suggest that, by reducing injection rate or shortening injection duration, the near‐term fraction of the surface injection converted to deep recharge is likely to be increased due to the narrowed groundwater mounding size, which would be limited by the water‐retarding effect of layer contrasts. This study has important implications for predicting and understanding multilayered groundwater mounding behaviours and associated water mass balance under the geologic stratification, and is expected to aid in optimizing the infiltration basin operation for aquifer recharge.

Modern silicon dynamics of a small high-latitude subarctic lake

Abstract. High biogenic silica (BSi) concentrations occur sporadically in lake sediments throughout the world; however, the processes leading to high BSi concentrations vary. We explored the factors responsible for the high BSi concentration in sediments of a small, high-latitude subarctic lake (Lake 850). The Si budget of this lake had not been fully characterized before to establish the drivers of BSi accumulation in this environment. To do this, we combined measurements of variations in stream discharge, dissolved silica (DSi) concentrations, and stable Si isotopes in both lake and stream water with measurements of BSi content in lake sediments. Water, radon, and Si mass balances revealed the importance of groundwater discharge as a main source of DSi to the lake, with groundwater-derived DSi inputs 3 times higher than those from ephemeral stream inlets. After including all external DSi sources (i.e., inlets and groundwater discharge) and estimating the total BSi accumulation in the sediment, we show that diatom production consumes up to 79 % of total DSi input. Additionally, low sediment accumulation rates were observed based on the dated gravity core. Our findings thus demonstrate that groundwater discharge and low mass accumulation rate can account for the high BSi accumulation during the last 150 cal yr BP. Globally, lakes have been estimated to retain one-fifth of the annual DSi terrestrial weathering flux that would otherwise be delivered to the ocean. Well-constrained lake mass balances, such as presented here, bring clarity to those estimates of the terrestrial Si cycle sinks.