Differences In Water Balance Research Articles

Impact of Agricultural Land Use Types on Soil Moisture Retention of Loamy Soils

Increasingly severe hydrological extremes are predicted for the Pannonian Basin as one of the consequences of climate change. The challenges of extreme droughts require the adaptation of agriculture especially during the intense growth phase of crops. For dryland farming, the selections of the optimal land use type and sustainable agricultural land management are potential adaptation tools for facing the challenges posed by increased aridity. To this end, it is indispensable to understand soil moisture (SM) dynamics under different land use types over drought-affected periods. Within the framework of a Slovenian–Hungarian project, soil moisture, matric potential and rainfall time series have been collected at three pilot sites of different land use types (pasture, orchards and a ploughland) in SW Hungary since September 2018. Experiments were carried out in soils of silt, silt loam and clay loam texture. In the summers (June 1 to August 31) of 2019 and 2022, we identified normal and dry conditions, respectively, with regard to differences in water balance. Our results demonstrated that soil moisture is closely controlled by land use. Marked differences of the moisture regime were revealed among the three land use types based on statistical analyses. Soils under pasture had the most balanced regime, whereas ploughland soils indicated the highest amplitude of moisture dynamics. The orchard, however, showed responses to weather conditions in sharp contrast with the other two sites. Our results are applicable for loamy soils under humid and subhumid temperate climates and for periods of extreme droughts, a condition which is expected to be the norm for the future.

Water balance in Japanese male kendo college athletes during training: a pilot study assessing seasonal differences with adjusted energy expenditure.

Due to various factors, water balance may vary across seasons. These effects may be particularly prominent in athletes and dependent upon energy expenditure during training. Japanese male kendo college athletes participated in this study during their training sessions. The participants were observed for three days each season, i.e., in spring, summer, and winter. The energy expenditure of the participants during training was monitored using the heart rate method. Data regarding the total amount of sweating, rate of sweating, amount of water intake, and rate of water intake were collected for each season and the differences were assessed using analysis of covariance, with energy expenditure as the covariate. The water balance parameter values observed during a kendo training session in summer were the highest, whereas these values were significantly reduced in winter. Energy expenditure was the highest in spring. The amount of sweating per energy expenditure varied seasonally, reaching as high as 2.14 g/kcal in summer. After adjusting for the influence of energy expenditure, the amount of sweating, amount of water intake, and water intake rate varied significantly by seasons, with the highest values in summer (P<0.001). The sweating rate was high in all the seasons, but the highest rate was observed in summer, followed by spring and then winter. There was a significant difference in the sweating rate in each season (P<0.001). The rehydration rate was 28% in spring, 39% in summer, and 22% in winter. After adjusting for the influence of energy expenditure, seasonal differences in water balance were observed in Japanese male kendo college athletes during training. These results suggest that water intake is essential after training in any season to maintain the water balance of the body.

Assessment of Water Balance and Traditional Surface Irrigation Practices in the Northern Nile Delta

Water balance analysis helps in managing water supply. Therefore, matching between water supply and demand is very important to overcome water shortage.This study aims at presenting comprehensive analysis to understand the nature of operating system in the traditional surface irrigation systems aiming to establish a comprehensive analysis to sustain the irrigation system, considering the problems of water supply, inequity, water quality deterioration, and poor irrigation and drainage management. Analysis in this study was done in two hubs. Firstly, study the parameters affecting water supply and demand; secondly, assessing water availability, adequacy, equity and distribution of irrigation during 24 hours’ cycle.The study area is located in Kafr El-Dawar irrigation district, El-Beheira governorate in the western part of the Nile Delta.The findings show that the differences in water balance per feddan (feddan is an Egyptian land unit equals 4206 m2) at all tertiary canals (meskas) are small; At the head of the canals, no night irrigation or drainage water reuse events during the irrigation seasons were observed; and the irrigation rotation is irregular. These findings elaborate that the location on the canal and the presence of subsurface drainage are mainly affecting the water balance in the study area.

Differences in water balance between grassland and forest watersheds using long-term data, derived using the CoupModel

Abstract To quantify the role of land cover during a period of climate change, the runoff response is studied for Plynlimon in Wales, UK. The main objective was two-fold: (i) to create a protocol for modeling water balance on a daily basis; and (ii) to describe the extent to which the impact of land-use changes can be identified and supported by the long-term monitoring data of runoff from two neighboring watersheds with different land covers. The process-oriented CoupModel platform was used to set up the model with a well-defined uncertainty for selected parameters. The behavioral ensembles were applied to simulated daily discharge data for the period of 1992–2010 using subjective criteria to reduce the prior 35,000 candidates with a random uniform distribution of 40 parameters. The accepted ensemble was reduced to 100 candidates by accepting the best root-mean-square error (RMSE) on the accumulated residuals during the simulation period. Similar good performance for the entire period and both watersheds was obtained. The differences in interception evaporation accounted for the most important differences between forest and grassland. The obtained residual demonstrated that changes in the forest cover had an impact on the water balance during the first part of the simulation period.

Differences in the water-balance components of four lakes in the southern-central Tibetan Plateau

Abstract. The contrasting patterns of lake-level fluctuations across the Tibetan Plateau (TP) are indicators of differences in the water balance over the TP. However, little is known about the key hydrological factors controlling this variability. The purpose of this study is to contribute to a more quantitative understanding of these factors for four selected lakes in the southern-central part of the TP: Nam Co and Tangra Yumco (increasing water levels), and Mapam Yumco and Paiku Co (stable or slightly decreasing water levels). We present the results of an integrated approach combining hydrological modeling, atmospheric-model output and remote-sensing data. The J2000g hydrological model was adapted and extended according to the specific characteristics of closed-lake basins on the TP and driven with High Asia Refined analysis (HAR) data at 10 km resolution for the period 2001–2010. Differences in the mean annual water balances among the four basins are primarily related to higher precipitation totals and attributed runoff generation in the Nam Co and Tangra Yumco basins. Precipitation and associated runoff are the main driving forces for inter-annual lake variations. The glacier-meltwater contribution to the total basin runoff volume (between 14 and 30 % averaged over the 10-year period) plays a less important role compared to runoff generation from rainfall and snowmelt in non-glacierized land areas. Nevertheless, using a hypothetical ice-free scenario in the hydrological model, we indicate that ice-melt water constitutes an important water-supply component for Mapam Yumco and Paiku Co, in order to maintain a state close to equilibrium, whereas the water balance in the Nam Co and Tangra Yumco basins remains positive under ice-free conditions. These results highlight the benefits of linking hydrological modeling with atmospheric-model output and satellite-derived data, and the presented approach can be readily transferred to other data-scarce closed lake basins, opening new directions of research. Future work should go towards a better assessment of the model-chain uncertainties, especially in this region where observation data are scarce.

Ecohydrology of Adjacent Sagebrush and Lodgepole Pine Ecosystems: The Consequences of Climate Change and Disturbance

Sagebrush steppe and lodgepole pine forests are two of the most widespread vegetation types in the western United States and they play crucial roles in the hydrologic cycle of these water-limited regions. We used a process-based ecosystem water model to characterize the potential impact of climate change and disturbance (wildfire and beetle mortality) on water cycling in adjacent sagebrush and lodgepole pine ecosystems. Despite similar climatic and topographic conditions between these ecosystems at the sites examined, lodgepole pine, and sagebrush exhibited consistent differences in water balance, notably more evaporation and drier summer soils in the sagebrush and greater transpiration and less water yield in lodgepole pine. Canopy disturbances (either fire or beetle) have dramatic impacts on water balance and availability: reducing transpiration while increasing evaporation and water yield. Results suggest that climate change may reduce snowpack, increase evaporation and transpiration, and lengthen the duration of dry soil conditions in the summer, but may have uncertain effects on drainage. Changes in the distribution of sagebrush and lodgepole pine ecosystems as a consequence of climate change and/or altered disturbance regimes will likely alter ecosystem water balance.

Effect of bedrock flow on catchment rainfall‐runoff characteristics and the water balance in forested catchments in Tanzawa Mountains, Japan

AbstractIn this paper, we examined the role of bedrock groundwater discharge and recharge on the water balance and runoff characteristics in forested headwater catchments. Using rigorous observations of catchment precipitation, discharge and streamwater chemistry, we quantified net bedrock flow rates and contributions to streamwater runoff and the water balance in three forested catchments (second‐order to third‐order catchments) underlain by uniform bedrock in Japan. We found that annual rainfall in 2010 was 3130 mm. In the same period, annual discharge in the three catchments varied from 1800 to 3900 mm/year. Annual net bedrock flow rates estimated by the chloride mass balance method at each catchment ranged from −1600 to 700 mm/year. The net bedrock flow rates were substantially different in the second‐order and third‐order catchments. During baseflow, discharge from the three catchments was significantly different; conversely, peak flows during large storm events and direct runoff ratios were not significantly different. These results suggest that differences in baseflow discharge rates, which are affected by bedrock flow and intercatchment groundwater transfer, result in the differences in water balance among the catchments. This study also suggests that in these second‐order to third‐order catchments, the drainage area during baseflow varies because of differences between the bedrock drainage area and surface drainage area, but that the effective drainage area during storm flow approaches the surface drainage area. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Patagonian ostracods as indicators of climate-related hydrological variables: implications for paleoenvironmental reconstructions in Southern South America

Different precipitation regimes across Patagonia generate an environmental gradient that is expected to reflect upon the solute composition and concentration of lake water through the ensuing differences in water balance. In turn, this hydrochemical gradient could influence the occurrence and distribution of ostracods in the area. A cluster analysis on hydrochemical data of 36 Southern Patagonian waterbodies shows that low salinity, bicarbonate-dominated waters characterize Andean and ecotonal lakes, located in the wetter part of the precipitation gradient, while their steppe counterparts, which receive a much lower precipitation input, are more saline, enriched in all major anions and sodium-dominated. Kruskal–Wallis tests followed by Mann–Whitney pairwise comparisons show statistically significant differences in the ostracod species each water type hosts, with L. patagonica, E. cecryphalium, P. smaragdina and P. incae being found in the more dilute waters characteristic of Andean and ecotonal lakes and Limnocythere rionegroensis in the mesohaline, evaporatively evolved waters typical of steppe lakes. Other species studied do not appear to have such distinct distributions, having been found throughout the range of conditions studied. These findings promote the use of the aforementioned ostracods as semi-quantitative paleohydrological indicators, which could improve paleoclimatic reconstructions in Patagonia.

Simulated water balance of forest and farmland in the hill and gully region of the Loess Plateau in China

Large-scale vegetation establishment has not only helped to prevent serious soil and water loss on the Loess Plateau of China but also led to reduced water availability and soil desiccation. Examining the water balance of forested and farmed land allowed us to determine water consumption of vegetation and understand the mechanisms of soil desiccation, important factors for the sustainable conversion of farmland to forest in this area. The effects of forests and crops on the water balance within the soil–vegetation–atmosphere system were studied using a coupled water and heat flow model known as “CoupModel”, which was calibrated on the basis of field measurements of soil water content, surface runoff, throughfall, stemflow, leaf area index, vegetation cover, canopy height and depth of root system in the hill and gully region of the Loess Plateau. Data were collected between 27 May 2006 and 31 October 2007. Two types of planted vegetation (acacia forest and farmland) in the Yan'gou watershed in the northern part of the Shaanxi Province were chosen to examine water transfer in the absence of soil texture (silt loam) differences and to explore the importance of vegetation type in relation to water balance. The simulations indicated that vegetation type and slope aspect significantly influenced the magnitude of every water balance component in the soil–vegetation–atmosphere system. Compared to forest, farming the land reduced interception (69.1–78.3%) and transpiration (37.3–40.4%), while increasing surface runoff by a factor of 5.0–40.2 and soil evaporation by 3.1–32.0%. Thus, farming resulted in 1.1–1.2 times more soil water storage than afforestation. Therefore, canopy interception and transpiration are responsible for soil desiccation in plantation forests. Simulation differences in water balance between acacia forest and farmland highlight that when converting farmland to forest on the Loess Plateau of China, tree species should be selected with care; this is particularly important on south-facing slopes.

Modelling the hydrological response of a Mediterranean medium-sized headwater basin subject to land cover change: The Cardener River basin (NE Spain)

Summary Abandonment of old agricultural fields is one of the main land cover changes over the second half of the XX century in Pyrenean headwater catchments, resulting in a natural succession from old crop fields and meadows towards shrub and forested covers, as well as an increase in forest canopy densities. In this situation, important changes in hydrological processes, water balance and, in consequence, water resources have been identified in the records and are expected for the future. The HYLUC model [Calder, I.R., 2003. Assessing the water use of short vegetation and forests: development of the Hydrological Land Use Change (HYLUC) model. Water Resources Research, 39(11), 1318] was tested for simulating the daily flows and water balance of the River Cardener (NE Spain) as well as for estimating the hydrological consequences of changes in land cover under operational conditions, i.e., with limited input data and parameter requirements. HYLUC successfully simulated the historical daily flows, flow duration curve and annual water balances in the catchment. It had several advantages over the hydrological model currently used for operational purposes in this catchment, although a snow cover sub-model should be added if it is to be applied to the main headwater catchments in the same Pyrenean region. When the model was used to simulate the consequences of land cover changes, the differences in water balance were larger than those predicted with an annual water balance equation. However, similar results were obtained from the analysis of historical data from headwater catchments of the Ebro River basin, and the decrease in low flows simulated under forest cover was comparable to that observed under Mediterranean climate elsewhere.

Is the strategy for cold hardiness in insects determined by their water balance? A study on two closely related families of beetles: Cerambycidae and Chrysomelidae

The strategy for cold-hardiness and water balance features of two closely related families of Coleoptera, Cerambycidae and Chrysomelidae, were investigated. Cerambycids were freeze-avoiding with low supercooling points, whereas chrysomelids froze at high temperatures and were tolerant to freezing. Hence, the two families have adopted different strategies for cold-hardiness. Due to their low trans-cuticular water permeability, the cerambycids have low rates of evaporative water loss. Chrysomelids have much higher trans-cuticular water permeability, but freezing brings their body fluids in vapour pressure equilibrium with ice and prevents evaporative water loss. The differences in cold-hardiness strategies and rates of water loss are likely to reflect the water content of the diets of the two families. Cerambycids feed on dry wood with low water content, causing a restrictive water balance. Chrysomelids feed on leaves with high water content and may use evaporation through the cuticle as a route of water excretion. Haemolymph ice nucleators help chrysomelids to freeze at a high temperature and thus to maximize the period they spend in the water saving frozen state. The diet-related differences in water balance may be the reason why the two families have developed different strategies for cold-hardiness.

Modelling the water balance of a mesoscale catchment basin using remotely sensed land cover data

Summary Hydrological modelling of mesoscale catchments is often adversely affected by a lack of adequate information about specific site conditions. In particular, digital land cover data are available from data sets which were acquired on a European or a national scale. These data sets do not only exhibit a restricted spatial resolution but also a differentiation of crops and impervious areas which is not appropriate to the needs of mesoscale hydrological models. In this paper, the impact of remote sensing data on the reliability of a water balance model is investigated and compared to model results determined on the basis of CORINE (Coordination of Information on the Environment) Land Cover as a reference. The aim is to quantify the improved model performance achieved by an enhanced land cover representation and corresponding model modifications. Making use of medium resolution satellite imagery from SPOT, LANDSAT ETM+ and ASTER, detailed information on land cover, especially agricultural crops and impervious surfaces, was extracted over a 5-year period (2000–2004). Crop-specific evapotranspiration coefficients were derived by using remote sensing data to replace grass reference evapotranspiration necessitated by the use of CORINE land cover for rural areas. For regions classified as settlement or industrial areas, degrees of imperviousness were derived. The data were incorporated into the hydrological model GROWA (large-scale water balance model), which uses an empirical approach combining distributed meteorological data with distributed site parameters to calculate the annual runoff components. Using satellite imagery in combination with runoff data from gauging stations for the years 2000–2004, the actual evapotranspiration calculation in GROWA was methodologically extended by including empirical crop coefficients for actual evapotranspiration calculations. While GROWA originally treated agricultural areas as homogeneous, now a consideration and differentiation of the main crops is possible. The accuracy was determined by runoff measurements from gauging stations. Differences in water balances resulting from the use of remote sensing data as opposed to CORINE were analysed in this study using a representative subcatchment. Resulting Nash–Sutcliff model efficiencies improved from 0.372 to 0.775 and indicate that the enhanced model can produce thematically more accurate and spatially more detailed local water balances. However, the proposed model enhancements by satellite imagery have not exhausted the full potential of water balance modelling, for which a higher temporal resolution is required.

Interpretation of results from on-farm experiments: manure-nitrogen recovery on grassland as affected by manure quality and application technique. 1. An agronomic analysis

In a 5-year field experiment, a comparison was made between the manure application practices of two adjacent dairy farms in the north of the Netherlands. Grassland management systems at Drogeham and Harkema contrasted in manure application technique (surface application versus shallow injection, respectively), quality of applied manure (slurry + MX: slurry with Euromestmix® clay mineral additive versus regular slurry), and some relevant site characteristics (high versus low soil organic matter content and soil moisture supply). Effects of manure types and application techniques, and treatment of the soil with a micro-organism supplement, were tested in a factorial experiment at the two sites, two blocks per site, one with and one without additional application of 157 kg N ha −1 year −1 inorganic fertilizer. Apparent N recovery was higher after shallow injection than after surface application. For plots receiving no additional inorganic fertilizer, this difference was largest for slurry + MX applied at site Harkema, since this slurry-site combination resulted in the highest observed average apparent N recovery following shallow injection (47%) and the lowest N recovery following surface application (20%). For plots receiving additional inorganic fertilizer N the contrasts between treatments were less pronounced. Year effects on N uptake and dry matter production could be related to cumulative temperature and precipitation surplus over the growing season. A simple comparison between the grassland management systems was carried out based on the response curves derived from the experiment. This demonstrated that the grassland system where slurry was applied by shallow injection is not necessarily the lowest in actual amount of N not accounted for (i.e., potentially lost). The efficiency of the Harkema system strongly depended on high N recovery, but showed high potential losses in some years and a high herbage crude protein content in other years, due to the low DM production capacity. On the other hand, the Drogeham system was tuned to high DM production and was characterized by higher system stability, as reflected by more stable relationships between DM production and N not accounted for and herbage crude protein content. These differences between the systems were probably to a large extent caused by differences in water balance and soil organic matter content.

Soil moisture and plant stress dynamics along the Kalahari precipitation gradient

We present an analysis of water balance and plant water stress along the Kalahari precipitation gradient using a probabilistic model of soil moisture. The rainfall statistical characteristics, obtained from daily data of four stations along the transect, show that the rainfall gradient (from 950 to 300 mm/year) is mostly due to a decrease in the mean rate of storm arrivals (from 0.38 to 0.09 1/day) rather than to a change in the mean storm depth (practically constant at 10 mm). Using this information and typical vegetation and soil parameters, the analysis relates the vegetation properties along the transect with those of climate and soil. It is shown that differences in water balance and plant water stress between trees and grasses generate varying preferences for vegetation types along the transect, with deeper‐rooted trees favored in the more mesic regions of the northern Kalahari and grasses favored in the drier zones of the southern Kalahari. The point of equal plant water stress is found at about 420 mm of rainfall during the growing season (October–April), indicating the possibility of tree‐grass coexistence in the central sector of the Kalahari. These findings are consistent with patterns of vegetation distribution across the Kalahari transect.

Climate, soil, and vegetation controls upon the variability of water balance in temperate and semiarid landscapes: Downward approach to water balance analysis

Observed differences between water balance for temperate and semiarid catchments can be attributed to variability in the primary controls of the soil profile (soil water storage capacity and permeability), vegetation (surface coverage and water use efficiency), and climate (rainfall and potential evaporation). Motivated by the downward development methodology mooted by Klemes [1983], this paper explores the underlying climate and landscape interactions that cause differences in water balance between a number of temperate and semiarid benchmark catchments around Australia. A systematic parsimonious analysis based around a simple water balance model whose parameters are estimated from available data is used to observe and interpret signatures of annual, intra‐annual, and daily water balance behavior and variability. The essence of the downward analysis is that model complexity evolves from the simplest form to its final quasi‐distributed framework with multiple storages and process interactions in response to inadequacies in signature prediction. Consequently, each step in the process develops insight into local climate and landscape influences and sensitivity to their temporal and spatial variabilities. The results affirm that the relative influence of climate and landscape properties upon catchment response is manifested in a systematic transformation of process sensitivity with increasing timescales (annual, monthly, daily, and hourly). Significantly, drier catchments are shown to be more sensitive to small‐scale perturbation than humid catchments. We conclude that the downward analysis approach is a means to better understand the significance of landscape variability upon catchment response. Consequential knowledge can begin to explain data requirements and requisite model complexity and to provide insight into the ability to reliably predict water balance behavior. These are important first steps toward the longer‐term objective of reliably predicting water balance variability across ungauged basins.

Use of modelling to explore the water balance of dryland farming systems in the Murray-Darling Basin, Australia

The Agricultural Production Systems Simulator (APSIM) modelling framework was used to explore components of the water balance for a range of farming systems in the Murray-Darling Basin (MDB) of Australia. Water leaking below the root zone of annual crops and pastures in this region is leading to development of dryland salinity and delivery of salt to waterways. Simulation modelling was used to identify the relative magnitude of transpiration, soil evaporation, runoff and drainage and to explore temporal variability in these terms for selected locations over the 1957–1998 climate record. Two transects were used to explore the impact of climate on water balance, with all other factors held constant, including the soil. An east–west transect at approximately latitude 33°S demonstrates the primary effect of annual average rainfall ranging from 300 to 850 mm. A north–south transect along approximately the 600 mm rainfall isohyet demonstrates a secondary effect of rainfall distribution, with the fraction of annual rainfall received in winter months rising from 40% in the north to 70% in the south. Water excess (i.e. runoff plus drainage) is strongly episodic, with 60% simulated to occur in 25% of years. Longer term cycles are also evident in the time series simulations, with strong below average periods from 1959–1968 and 1979–1988 interspersed with extended periods of above average water excess from 1969–1978 and 1989–1993. Water excess was highest for the annual wheat farming system and lowest for perennial lucerne pasture. Other systems that mix summer and winter annuals (opportunity cropping) or include wheat and lucerne pasture in different temporal combinations (phase farming and companion cropping) were intermediate in their simulated water excess. These differences in water balance of the farming systems simulated were associated with differences in grain and forage yields that will affect their economic viability. The predictions of annual water excess derived from the dynamic, daily time-step modelling using APSIM for a wheat based farming system were of similar magnitude as those predicted by the Zhang et al. (2001) static model for shallow rooted pasture catchments, whilst continuous lucerne was similar to predictions for deep rooted forest catchments. To capture the effect of rainfall distribution between winter and summer an additional term was added to the Zhang model. This modified function captured 88% of the variation in the APSIM predictions of annual average water excess from annual wheat systems for 78 locations in the MDB.

Modeling water balance components in relation to field layout in lowland paddy fields. II: Model application

In a companion paper, the development of a water balance model to predict the changes in water balance components in relation to field layout in lowland paddy fields was outlined. In this study, the model was applied to a large irrigated area to assess and compare the water balance of intensive and extensive field layouts. The results show significant differences in water balance which are attributed to the layouts and water management practices. The field layouts influenced the equity of water allocation, effective rainfall, water use efficiencies and relative proportion of various water balance components. Eight indices are computed to evaluate the effects of layout under different land and hydrological conditions. Appropriate measurement scales for ranking the indices are proposed.

Simulated water balance of Scots pine stands in Sweden for different climate change scenarios

The effects of climate change on the water balance of Scots pine were studied with a coupled water and heat flow model called ‘SOIL’. Two forest soil types (a silty-sand and a sand) at five locations in Sweden were chosen to represent sites with different air temperature, growing season length and precipitation excess. The simulated water balance for the period 1961–1987 was compared with those simulated with two climate change scenario schemes: one is based on increased temperature and the other on both increased temperature and increased precipitation. Different assumptions regarding the effects of changes in leaf area index and minimum canopy resistance on transpiration were studied. Water stress increased substantially in the scenarios based on increased temperature only, which prevented transpiration from increasing. But with scenarios based on simultaneous changes in temperature and precipitation, water stress increased mainly during spring and transpiration increased by 50 mm and 100 mm in northern and southern Sweden, respectively, i.e. by 30–50%. When simultaneous changes in climate and stand characteristics were assumed, transpiration increased by 30–70% with the relative change being greatest for northern Sweden. Differences in water balance between the locations and soil types were less pronounced in the climate change scenarios than in the present climate scenario.

Variations in Water Balance and Recharge Potential at Three Western Desert Sites

AbstractRadioactive and hazardous waste landfills exist at numerous desert locations in the USA. At these locations, annual precipitation is low and soils are generally dry, yet little is known about recharge of water and transport of contaminants to the water table. Recent water balance measurements made at three desert locations, Las Cruces, NM, Beatty, NV, and the U.S. Department of Energy's Hanford Site in the state of Washington, provide information on recharge potential under three distinctly different climate and soil conditions. All three sites show water storage increases with time when soils are coarse textured and plants are removed from the surface, the rate of increase being influenced by climatic variables such as precipitation, radiation, temperature, and wind. Lysimeter data from Hanford and Las Cruces indicate that deep drainage (recharge) from bare, sandy soils can range from 10 to &gt;50% of the annual precipitation. At Hanford, when desert plants are present on sandy or gravelly surface soils, deep drainage is reduced but not eliminated. When surface soils are silt loams, deep drainage is eliminated whether plants are present or not. At Las Cruces and Beatty, the presence of plants eliminated deep drainage at the measurement sites. Differences in water balance between sites are attributed to precipitation quantity and distribution and to soil and vegetation types. The implication for waste management at desert locations is that surface soil properties and plant characteristics must be considered in waste site design in order to minimize recharge potential.

Experiments on the water budget of densely and sparsely needled spruces [Picea abies (L.) Karst.] in a declining stand

The osmotic potentials of needles were compared from numerous trees that had been classified according to needle loss along an altitude profile. With the increasing degree of damage of the trees, the maximum and minimum values deviated more strongly above and below the common mean of all samples. The level of water content of the needles unequivocally reflected the vitality of the trees. Experiments covering a whole vegetation period were performed on a tree pair selected from a natural stand. They were designed to demonstrate differences in water balance between the “healthy” and “damaged” state of the trees. For the “damaged” tree, measurements of the water potentials of single needles showed a greater reduction of potential during the course of the day compared to the “healthy” tree. Recovery in the evenings was slower and often incomplete. The osmotic potentials of “damaged” and “healthy” shoots measured in individual needles also differed both predawn and especially after transpiration stress. Depending on weather and soil desiccation, the differences were more or less pronounced. In the “damaged” tree, the rises in potential after saturation of the twigs fell far short of the “healthy” tree. Reduction of water potential, osmotic potential and relative water content under comparable stress conditions suggest a reduced tolerance of drought by damaged trees. In the context of earlier experiments this result was ascribed to a lack of stomatal control, and long-term pollution effects were thus explained as a specific disturbance of hydroregulation.