Daily Water Flux Research Articles

Monitoring of carbon-water fluxes at Eurasian meteorological stations using random forest and remote sensing

Simulating the carbon-water fluxes at more widely distributed meteorological stations based on the sparsely and unevenly distributed eddy covariance flux stations is needed to accurately understand the carbon-water cycle of terrestrial ecosystems. We established a new framework consisting of machine learning, determination coefficient (R2), Euclidean distance, and remote sensing (RS), to simulate the daily net ecosystem carbon dioxide exchange (NEE) and water flux (WF) of the Eurasian meteorological stations using a random forest model or/and RS. The daily NEE and WF datasets with RS-based information (NEE-RS and WF-RS) for 3774 and 4427 meteorological stations during 2002–2020 were produced, respectively. And the daily NEE and WF datasets without RS-based information (NEE-WRS and WF-WRS) for 4667 and 6763 meteorological stations during 1983–2018 were generated, respectively. For each meteorological station, the carbon-water fluxes meet accuracy requirements and have quasi-observational properties. These four carbon-water flux datasets have great potential to improve the assessments of the ecosystem carbon-water dynamics.

The effect of manganese(II) on recharge clogging of groundwater heat pump

In order to obtain the mechanism of recharge clogging in the case of manganese ion(Mn2+), the effects of Mn2+ on recharge clogging and microbial community were studied in laboratory sand column. Comparative experiments with four concentrations of Mn2+ were performed. The process of recharge was simulated twice a day, and the daily water flux was detected. The microbial quantity was detected after sand column clogging at 20d, and the microbial structure was analyzed at the end of experiment. The results showed that Mn2+ had little effect on recharge clogging and promoted the growth of microorganisms. The dominant microorganisms in sand column were Flavobacterium sp., Pseudomonas sp., Janthinobacterium sp., and unclassified Comamonadaceae. Manganese ions improved the competitiveness of Flavobacterium sp., but Pseudomonas sp., unclassified Comamonadaceae, Janthinobacterium sp. were inhibited under high manganese concentration.

Effects of temperature and salinity on body fluid dynamics and metabolism in the estuarine diamondback terrapin (Malaclemys terrapin).

The diamondback terrapin is the only temperate turtle species that exclusively inhabits estuarine environments. Morphological, behavioral and physiological features contribute to the terrapin's ability to regulate body fluid osmotic pressure in a euryhaline environment. Low integument permeability combined with aquatic-terrestrial shuttling behavior limits passive exchange of water and salts with the environment, and terrapins regulate active uptake of salts via alterations in drinking and feeding behavior. The lachrymal salt gland facilitates excretion of excess sodium (Na+) and chloride (Cl-) ions through active transport mechanisms. We investigated body fluid dynamics, oxygen consumption (V̇O2 ) and osmotic status of terrapins exposed to an acute increase in salinity (12 to 35 psu) at 10 and 25°C to gain insight into the relative importance of behavioral versus physiological osmoregulatory adjustments over a range of seasonally relevant temperatures. Linear mixed models were used to evaluate the effects of experimental temperature, salinity and mass. Overall, temperature effects were stronger than salinity effects. Terrapins acclimated to 25°C had significantly lower blood osmolality and Na+, and higher water turnover rates, daily water flux (DWF) and V̇O2 compared with terrapins acclimated to 10°C. Salinity effects were restricted to DWF, which significantly decreased in response to acute exposure to 35 psu. Our results support the notion that behavioral adjustments predominate in the osmoregulatory strategy of terrapins.

Water and energy fluxes during summer in an arid‐zone passerine bird

Endothermic animals resident in hot, arid terrestrial environments are likely to face a trade‐off between their ability to obtain water and elevated thermoregulatory water requirements. We assessed whether daily water flux (DWF) is higher on hot days, reflecting increases in evaporative cooling demands, in an arid‐zone bird that obtains its water through food intake. We obtained measurements of DWF (partitioned into water influx and efflux rates) in 71 White‐browed Sparrow‐Weavers Plocepasser mahali at a desert site and a semi‐desert site, during summer in the Kalahari Desert of southern Africa. We found no evidence that DWF varied with maximum daily air temperature (Tair, range = 27.6–39.2 °C). Instead, DWF was lower during dry periods than in the wet season at the semi‐desert site. Furthermore, birds showed deficits in water balance (water influx/water efflux) during the dry periods at both sites. Our data show that DWF is low in a non‐drinking bird that obtains its water through food, and that demands for evaporative water loss on very hot days (maximum Tair of 40–44 °C) may exceed water intake rates during hot and dry periods. Species that do not have opportunities to drink will experience strong trade‐offs between thermoregulation, hydration state and activity levels as temperatures increase.

Total body water and water turnover rates in the estuarine diamondback terrapin (Malaclemys terrapin) during the transition from dormancy to activity.

Water and salt concentrations in an animal's body fluids can fluctuate with changing environmental conditions, posing osmoregulatory challenges that require behavioral and physiological adjustments. The purpose of this study was to investigate body water dynamics in the estuarine diamondback terrapin (Malaclemys terrapin), a species that undergoes seasonal dormancy in salt marsh habitats. We conducted a field study to determine the total body water (%TBW), water turnover rate (WTR) and daily water flux (DWF) of female terrapins in south eastern North Carolina pre- and post-emergence from winter dormancy. Terrapins were injected with [(2)H]deuterium on two occasions and washout of the isotope was monitored by taking successive blood samples during the period of transition from dormancy to activity. The WTR and DWF of dormant terrapins were significantly lower than those of active terrapins (WTR(dormant)=49.70±15.94 ml day(-1), WTR(active)=100.20±20.36 ml day(-1), DWF(dormant)=10.52±2.92%TBW day(-1), DWF(active)=21.84±7.30%TBW day(-1)). There was no significant difference in %TBW between dormant and active terrapins (75.05±6.19% and 74.54±4.36%, respectively). The results from this field study provide insight into the terrapin's ability to maintain osmotic homeostasis while experiencing shifts in behavioral and environmental conditions.

A revised land hydrology in the ECMWF model: a step towards daily water flux prediction in a fully‐closed water cycle

AbstractThe ECMWF land surface hydrology has been revised in the last 3 years in its soil and snow hydrological components, leading to improvements in weather and seasonal predictions. It has been shown that efforts devoted to the improvement of land surface processes can lead to a more accurate representation of the global water cycle on monthly timescales. In this paper, we analyse the impact of land hydrology revisions at daily timescales on both atmospheric near‐surface quantities and river discharges by coupling the ECMWF land surface model (HTESSEL) to a river routing scheme total runoff integration pathways (TRIP2). This application defines a hydro‐meteorological verification for land surface models and it shows the usefulness of river discharge observations for quantitative evaluation of the global water cycle at daily timescales. The relative contributions of the soil and snow hydrology revisions on atmospheric state, in particular for temperature, and the predicted river discharge are evaluated showing a significant incremental performance with the land surface updates. Copyright © 2010 John Wiley & Sons, Ltd.

A sampling strategy for estimating plot average annual fluxes of chemical elements from forest soils

A sampling strategy for estimating spatially averaged annual element leaching fluxes from forest soils is presented and tested in three Dutch forest monitoring plots. In this method sampling locations and times (days) are selected by probability sampling. Sampling locations were selected by stratified random sampling with five blocks of equal surface area as strata. At each selected day six composite soil solution samples were collected, consisting of five aliquots of equal volume, one per stratum. For most sampling days at some locations no soil solution was collected (non-response), and as a result the average of the six composite sample concentrations (the naïve estimator) is a biased estimator of the plot mean concentration. The plot mean concentration at these days was estimated by ordinary least squares. This estimation method eliminates the bias of the naïve estimator. This estimated concentration was multiplied by the modeled water flux to obtain an estimate of the daily element leaching flux. Sampling times (days) were selected by systematic πps-sampling (sampling with probabilities proportional to size), with precipitation surplus, averaged over the past 30 years, as a measure of size. The spatially averaged annual leaching flux was estimated by the ratio-estimator, accounting for the selection probabilities of the days, using the modeled daily water flux as an auxiliary variable.

Impacts of sampling design and estimation methods on nutrient leaching of intensively monitored forest plots in the Netherlands

Element fluxes through forest ecosystems are generally based on measurements of concentrations in soil solution at regular time intervals at plot locations sampled in a regular grid. Here we present spatially averaged annual element leaching fluxes in three Dutch forest monitoring plots using a new sampling strategy in which both sampling locations and sampling times are selected by probability sampling. Locations were selected by stratified random sampling with compact geographical blocks of equal surface area as strata. In each sampling round, six composite soil solution samples were collected, consisting of five aliquots, one per stratum. The plot-mean concentration was estimated by linear regression, so that the bias due to one or more strata being not represented in the composite samples is eliminated. The sampling times were selected in such a way that the cumulative precipitation surplus of the time interval between two consecutive sampling times was constant, using an estimated precipitation surplus averaged over the past 30 years. The spatially averaged annual leaching flux was estimated by using the modeled daily water flux as an ancillary variable. An important advantage of the new method is that the uncertainty in the estimated annual leaching fluxes due to spatial and temporal variation and resulting sampling errors can be quantified. Results of this new method were compared with the reference approach in which daily leaching fluxes were calculated by multiplying daily interpolated element concentrations with daily water fluxes and then aggregated to a year. Results show that the annual fluxes calculated with the reference method for the period 2003-2005, including all plots, elements and depths, lies only in 53% of the cases within the range of the average +/-2 times the standard error of the new method. Despite the differences in results, both methods indicate comparable N retention and strong Al mobilization in all plots, with Al leaching being nearly equal to the leaching of SO(4) and NO(3) with fluxes expressed in mol(c) ha(-1) yr(-1). This illustrates that Al release, which is the clearest signal of soil acidification, is mainly due to the external input of SO(4) and NO(3).

Modelling denitrification at the catchment scale

The objective of this work was to evaluate the importance of heterotrophic denitrification in the fate of nitrogen surpluses at the catchment scale. For that purpose we modified the denitrification module of TNT2 model and calibrated the model on a small catchment where denitrification measurements had been performed in different locations. The main interest of the TNT2 model is its ability to simulate the dynamics of the zones where soil and shallow water table interact, making it possible to spatialize the denitrification process. Daily water and nitrogen flux at the outlet were relatively well simulated (Nash of 0.85 and 0.77). In average, the model correctly simulates the denitrification measurements ( R = 0.68). Nitrogen flux towards the atmosphere, at the catchment scale (4.70 g N m − 2 year − 1 ), is of the same order of magnitude as the soluble N flux in the stream. The model was able to reproduce the distribution of denitrification in the riparian (mean of 9.26 g N m − 2 year − 1 ) and hillslope (mean of 3.45 g N m − 2 year − 1 ) domains of the catchment. The results confirm the importance of riparian denitrification, but show also that hillslope soils contribute significantly (60%) to the whole catchment denitrification. The variations of denitrification rates, and also of nitrate concentrations in stream were not very well simulated by the model, highlighting the complexity of the spatial and temporal controls of nitrogen dynamics in areas with high inputs of nitrogen fertilizers, especially under organic forms.

Comment on “Theoretical Analysis of Soil and Plant Traits Influencing Daily Plant Water Flux on Drying Soils” by T.R. Sinclair. Agron. J. 97:1148–1152 (2005)

Comment on “Theoretical Analysis of Soil and Plant Traits Influencing Daily Plant Water Flux on Drying Soils” by T.R. Sinclair. Agron. J. 97:1148–1152 (2005)

Nitrogen Behaviour and Nitrous Oxide Emission in the Tidal Seine River Estuary (France) as Influenced by Human Activities in the Upstream Watershed

The Seine River estuary (France) is the receptacle of a drainage basin characterised by high population density, heavy industrial activity and intensive agriculture. Whereas nitrate concentrations are high due to diffuse sources in the upstream drainage basin, ammonium mainly originates from the effluents of the Acheres wastewater treatment plant (WWTP) downstream from Paris and its suburbs (6.5 million equivalent-inhabitants). Ammonium is mostly nitrified in the tidal freshwater estuary and nitrification causes a strong summer oxygen deficit. Average longitudinal summer profiles of oxygen and nitrogen concentrations for two periods, between 1993–1997 and 1998–2003 in dry hydrological conditions (excluding the wet years 2000 and 2001) clearly reflect the changes due to the improved treatment of wastewater from Paris and its suburbs. On the basis of daily water flux data and twice monthly nitrogen measurements at the boundaries of the upstream freshwater estuarine section (108 km), we calculated nitrification and denitrification fluxes, whose annual averages were 43 and 71 × 103 kg N d−1 respectively from 1993 to 2003, with summer values (July–September) representing 73 and 57% of the annual fluxes, respectively. The degree of denitrification in the upper estuary appears to be closely related to the nitrification, itself more loosely related to the amount of reduced nitrogen (Kjeldahl) brought by the treated effluents from the Acheres WWTP. We estimated the total N2O emissions to about 40 kg N d−1 (25–60 kg N d−1) in the same sector.

Blood-sucking bugs as a gentle method for blood-collection in water budget studies using doubly labelled water

During doubly-labelled water (DLW) experiments, blood collection by venous puncture may traumatize animals and consequently affect the animals' behaviour and energy budget. Recent studies have shown that blood-sucking bugs (Triatominae; Heteroptera) can be used instead of conventional needles to obtain blood from animals. In this paper, we validate the bug method in captive nectar-feeding bats, Glossophaga soricina, for water budget analysis by comparing the daily water flux estimated with the DLW method with values measured by an energy balance method. As the mean daily water flux of the DLW method was not significantly deviating from the expected value, blood-sucking bugs may substitute more invasive methods of blood collection in DLW experiments. Based on the DLW estimates, daily energy and water intake rates were calculated and compared to values measured with the energy balance method. The DLW method and the energy balance method yielded on average similar results regarding the daily energy intake (DLW method: 48.8+/-14.2 kJ d(-1) versus energy balance method: 48.1+/-9.9 kJ d(-1)) and daily water intake (DLW method: 13.7+/-2.4 mL d(-1) versus energy balance method: 14.7+/-3.0 mL d(-1)). Based on the calculated water and sugar intake per day, we estimated the sugar concentration of ingested nectar to equal on average 16.2+/-2.4% (mass/mass), which fell close to the measured sugar concentration of 17% (mass/mass) bats fed on during the experiment. We conclude that it is possible to extrapolate mean daily energy and water intake for animal groups, populations and species based on DLW estimates, but due to the large variance of results (low accuracy), it seems inadequate to calculate values for single individuals.

Theoretical Analysis of Soil and Plant Traits Influencing Daily Plant Water Flux on Drying Soils

Experimental evidence has been accumulating for a number of years that daily transpiration rates respond to the progressive drying of soil in a similar manner across a wide range of conditions when expressed as a function of available volumetric soil water content. There is little decrease in gas exchange until only about one‐third of the available soil water remains in the soil, and then gas exchange decreases in a nearly linear manner until the available soil water is exhausted. There exists no theoretical derivation that explicitly provides a basis for explaining the consistency in this response observed over a wide range of conditions. A relatively simple derivation is presented by defining plant water flux on drying soil relative to a plant on well‐watered soil and by examining the response in the relevant range of soil volumetric water content. This derivation resulted in a relatively simple expression that predicted daily transpiration rate response to drying soil that was consistent with experimental observations. Further, the results of this analysis showed the response was essentially independent of root length density, transpiration rate, and soil depth. Also, large decreases in soil hydraulic conductivity as the soil dries had only modest influences on the daily transpiration rate response. Expression of relative transpiration as a function of volumetric soil water content available to support transpiration also minimized the influence of soil texture on the overall response of water flux to drying soil. The derivation offers a theoretical basis to explain the stability in daily transpiration response to drying soil that has been observed over a wide range of conditions.

Water economy of free-living desert animals

Deserts are relatively dry and dehydrating places, by definition, but desert animals are composed of 65–75% water, just like non-desert animals. Do desert animals maintain water balance and body hydration level by conserving water better (decreasing output, as compared with non-desert species) or by getting more water each day (increasing input), or both? These questions can be evaluated with measurements of daily water flux rates (in ml/day) as determined with isotopically labeled water through free-ranging animals that are maintaining constant body masses. Inspection of the many field measurements now available reveals great variation (10 million-fold among terrestrial vertebrates alone), due largely to differences in body mass, but also due to taxonomic affinity (endothermy vs. ectothermy), season, diet and age, as well as to variation in habitat aridity. Fortunately, water flux rates can be normalized for much of this variation by dividing them by field metabolic rates, to yield units of ml water used per kJ energy metabolized (termed Water Economy Index, WEI). The WEI values of desert-dwelling eutherian mammals are significantly lower than in non-desert eutherians, and (surprisingly) desert endotherms have lower WEIs than desert ectotherms. Year-round WEI measurements on desert kangaroo rats, which have the lowest index yet measured, revealed that they often obtained more water than was available just from dry seeds, not by drinking, but by eating young green vegetation when available in spring, and especially by hydrating dry seeds before consumption by storing them in humid burrows for a while.

Assessment of the effects of spatial resolutions on daily water flux simulations

Impacts of spatially distributed precipitation and soil heterogeneity on modeling water fluxes at different spatial resolutions are investigated using the Three-layer Variable Infiltration Capacity (VIC-3L) land surface model at the Blue River watershed in Oklahoma. In this study, hourly grid-based NEXRAD (Next Generation Radar) Stage III radar precipitation data approximately at 4×4 km 2 resolution are used to compute daily precipitation at spatial resolutions of 1/32, 1/16, 1/8, 1/4, 1/2 and 1 degree based on an area weighted average method. Soil parameters at the corresponding six spatial resolutions are derived from the State Soil Geographic (STATSGO) soil data. The forcing data of daily maximum and minimum temperature, wind speed, and vegetation parameters are disaggregated/aggregated directly to finer/coarser spatial resolutions based on the University of Washington (UW) data, which are gridded at 1/8 degree spatial resolution. Our study suggests that a critical spatial resolution for the VIC-3L model may exist for the study watershed. For spatial resolutions finer than the critical resolution, one does not necessarily obtain better model performance in terms of runoff, evapotranspiration, and total zone soil moisture with increasing spatial resolution if the VIC-3L model parameters are calibrated at each spatial resolution. Also, model parameters calibrated at a coarse resolution can be applied to finer resolutions to obtain generally comparable results. However, model parameters calibrated at finer resolutions cannot result in comparable results when applied to resolutions coarser than the identified critical resolution. In addition, while soil moisture of the total zone is more sensitive to the spatial distributions of soil properties, runoff and evaporation are more sensitive to the spatial distribution of daily precipitation at the watershed being studied.

Seasonal and interindividual variation in field water metabolism of female meadow voles Microtus pennsylvanicus.

We analyzed variations in water flux rates on a large sample of meadow voles (Microtus pennsylvanicus) to quantify the effect of season on water metabolism of individuals and to examine patterns of intra- and interindividual variability. Voles were nonreproductive females maintained in outdoor enclosures where they fed on natural vegetation. They were injected one to three times with doubly labeled water, which resulted in one to six measures of daily water flux rate per individual. Summer water flux rates of voles were 258% of the predicted values for herbivorous eutherian mammals of similar size. To date, very few studies have focused on mammals with such high water flux rates. Body water volume of individuals was higher in summer than in winter (75.6% vs. 72.5%), and water flux rate of animals was 12.5% higher in the winter season (0.99 vs. 0.88 mL H2O g-1 d-1). Between-season differences in water fluxes were proportional to differences in energy expenditures, hence the water economy index remained constant across seasons (0.30 mL H2O kJ-1). Intraindividual variability of water flux rate was high compared to interindividual variability (repeatability, r<0.30), which will make it difficult to study natural selection of water metabolism in a microevolutionary framework, at least in meadow voles.

Frequency distribution of water and solute transport properties derived from Pan sampler data

Modeling of water and solute movement requires knowledge of the nature of the spatial distribution of transport parameters. Only a few of the field experiments reported in the literature contained enough measurements to discriminate statistically between lognormal and normal distributions. To obtain statistically significant data sets, six field experiments at four different sites were performed. Different degrees of macropore and matrix flow occurred at each site. In each experiment a solute pulse was added followed by artificial or natural rainfall. Sixteen thousand spatial distributed fluxes and solute concentrations were collected with wick and gravity samplers. Spatial distributions of solute velocity, dispersion coefficient, water flux, and solute concentration were determined over different timescales ranging from 1 hour to the duration of the experiment. A chi‐square test was used to discriminate between the type of frequency distributions. The spatially distributed water and solute transport parameters when averaged over the experimental period were found to fit the lognormal distribution when macropore flow dominates. Otherwise, when only matrix flow occurs a normal distribution fitted the data better. Under no‐till cultivation, hourly concentration and water flux are lognormally distributed, while tillage makes the tracer concentration to be normally distributed. Spatial frequency distributions of daily solute concentration change in time: Concentrations were normally distributed when the bulk of the solute broke through with the highest concentrations and lognormally distributed in the beginning and end of the experiment. Daily water flux was found to be lognormally distributed throughout the experiment, but the distribution varied between water applications: Shortly after water application, when wick and gravity pan samplers collected water predominantly from macropores and normally distributed at later times when mostly matrix pores were sampled with wick pan samplers.

Defecation, apparent absorption efficiency, and the importance of water obtained in the food for water balance in captive brown long‐eared (Plecotus auritus) and Daubenton's (Myotis daubentoni) bats

Mean apparent dry mass absorption efficiency by P. auritus fed on mealworms was 0.853 (S.D.=0.4, n=43). Mean apparent energy absorption efficiency by P. auritus and M. daubentoni fed on mealworms was 0.90 (S.D.=0.007, n=8). The mean energy content of mealworms was 28.6 kJ.g‐1 dry mass (S.D.=1.1, n=8), and that of faeces was 19.5 kJ.g‐1 (S.D.=0.7, n=8) in P. auritus and 19.9 kJ.g‐1 (S.D.=1.3, n=8) in M. daubentoni. Water content of mealworms was 61.1% wet mass (S.D.=1.4, n=173); water content of faeces was 73.3% in P. auritus (S.D.=6.8, n=76) and 72.3% (S.D.=7.0, n=42) in M. daubentoni. Oven‐dried mealworms consisted of &lt;1% ash, &lt;1% carbohydrate, 31% lipid and 39% protein. We suggest that the dry mass unaccounted for (28%) represented chitin, of which 59% was apparently absorbed during digestion. Apparent absorption by mass of both lipid and protein by P. auritus fed on mealworms was greater than 90%. Cumulative post‐prandial defecation was sigmoidal in both bat species with 50% (by mass) of faeces being voided within 4 h and 95% within 12 h of feeding. On the basis of previous measurements, using doubly‐labelled water, of daily energy expenditure and water flux in free‐living P. auritus, we predict that water intake via the food, as free water and as potential metabolic water, represents 20 to 40% of total daily water flux for P. auritus during lactation in the wild.

Water flux and mass gain during lactation in free‐living ringed seal (Phoca hispida) pups

Three ringed seal (Phoca hispida) pups were used to calculate water flux and milk intake, based on mass increase and dilution of injected tritiated water. Biological half life of tritium in ringed seal pups was 130 ± 17 h (mean ± S.D.). The plateau level of the isotope indicating equilibrium with the body water was, in all cases (N = 8), reached before the first blood sample was collected after 0·5 h. Daily water flux in the pups was 62·9 ± 21·5 ml kg‐1. Estimated daily milk intake of 1103 ± 388 ml milk resulted in a mass increase of 386 ± 104 g. Neonates had a fat content of 4·75%, and a water content of 70·1% (N = 3). Corresponding figures for a pup close to weaning were 36·5% and 46·3%. Isotope dilution calculations of body water gave an overestimate of 1·6% compared with body water content from desiccation. Ringed seal milk was found to contain 38·1% fat, 9·9% protein, 2·3% lactose and 1% ash.

Daily Energy Expenditure and Water Flux of Free-Living Blanford's Foxes (Vulpes cana), a small Desert Carnivore

The Blanford's fox, Vulpes cana (Blanford 1877) is a small canid (mean body mass = 956 g) that inhabits rocky mountains and canyons in the deserts of Israel, where it feeds mainly on invertebrates and fruits. We hypothesized that the energy expenditure of Blanford's foxes would be higher than that of a small canid that inhabits flat terrain, all else being equal. To test this hypothesis, we measured daily energy expenditure and water intake of freeliving Blanford's foxes and compared the results with those of the kit fox, Vulpes macrotis (Say 1823)