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Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Egypt's water resources face challenges arising from escalating urban demand, changes in land use, environmental requirements, and the impacts of climate change. To address these challenges, the study develops a dynamic model using WEAP model as a decision support tool for water sector planning and management. By comparing different scenarios, the research examines the benefits of water conservation in terms of cost reduction in supply, wastewater generation, and treatment. Considering the projection period until 2037, it is imperative to carefully examine the research findings and explore opportunities for further optimizing water use efficiency. Based on the model simulation results, it is anticipated that the total water demands in Egypt will rise from 78.40 billion cubic meters (BCM) in 2023 (comprising 61.10 BCM for the agricultural sector, 12.58 BCM for the municipal sector, and 5.73 BCM for the industrial sector) to 81.02 BCM in 2037. The water demand for the agricultural sector is projected to decrease from 61.30 billion cubic meters (BCM) in 2023 to 60.14 BCM in 2037 as a result of the implementation of modern and smart irrigation systems. Conversely, the municipal sector is expected to experience an increase from 12.58 BCM in 2023 to 14.88 BCM in 2037. Furthermore, for the industrial sector, the water demand is anticipated to rise from 5.73 BCM in 2023 to 6.00 BCM in 2037. [ABSTRACT FROM AUTHOR]

Development of different strategies for sustainable water management is very important in arid region of Punjab - Pakistan having 280km2 area. In this research, water budget is estimated using the hydrologic water balance equation in Bahawalpur district in Punjab. Initially, landcover of the study area is determined using the Geographic Information System (GIS) and remote sensing. Due to excess rainfall and mostly grown crop in the study area, 4 scenarios were made, (1) 70% of sugarcane area is changed into wheat (2) 70% of sugarcane area is changed into wheat and cotton (3) 50% of sugarcane is changed into orchard (citrus) and 30% of sugarcane is changed into wheat (4) Construction of artificial ponds for storage of excess rainfall. Observed evapotranspiration is estimated using the Cropwat model, which is changed into the potential evapotranspiration for all the scenarios. Average annual rainfall in 2015 was 511.3mm in 51 events, with evapotranspiration of 4.29mm/day resulting in 366.34mm excess water. For estimation of precipitation recharge, runoff is estimated using the Hydrological Engineering Center - Hydrological Modelling System (HEC - HMS). The model was calibrated and validated for year 1996 and 1997 respectively, and runoff was estimated from 1998 to 2015. Streamflow (3L and 4L distributaries) recharge is estimated by using the average hydraulic conductivity value and interpolated on total length of distributaries. Groundwater recharge is estimated by adding precipitation recharge and stream flow recharge. Data of total number of pumping wells is taken from Agricultural Department, Punjab. Total groundwater pumpage is estimated for pumping rate of each well. Water budget for all 3 scenarios is estimated by subtracting groundwater recharge to groundwater pumpage. Actual groundwater levels were measured in the study area. Water budget is compared with the actual groundwater levels which show that our calculations are correct. Result shows that 102,575,200m3 of water can be saved annually for an area of 280km2. This study also concluded that annual average water deficit is -2.138m, -2.117m, -2.128m and -2.064m for actual condition, scenario 1, scenario 2 and scenario 3 respectively. For rainwater storage, about 7,000 artificial ponds can be constructed having capacity of 15,000m3. This water will not only cover the irrigation requirement but also decrease the threat to groundwater depletion. If these ponds are not constructed, then scenario 3 has the lowest water extraction rate and should be adopted in this region for proper water management. [ABSTRACT FROM AUTHOR]

Copyright of Atmosphere -- Ocean (Taylor & Francis Ltd) is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

While early efforts to reduce external phosphorus (P) loads to Lake Erie eliminated the worst eutrophication symptoms in the 1970s and 1980s, the observed intensification of these symptoms in recent decades is difficult to explain by changes in the external P loading alone. We hypothesized that, in addition to external inputs, in-lake processes that release P to the water column may be contributing to the re-eutrophication of Lake Erie. Directly measuring these internal inputs is challenging and their scaling up to the entire lake system remains fraught with uncertainty. To constrain the magnitude of the net P input associated with in-lake processes, we generated a long-term annual total P (TP) budget for the Lake St. Clair–Lake Erie system, averaged over a 14-year period, from 2003 to 2016. The budget shows that the TP output from the system substantially exceeds the sum of the external TP inputs. To balance the budget, we estimate that in-lake processes add a net internal TP load of 3783 metric tons per year (MTA) to the water column. In comparison, the mean yearly external TP load to the Lake St. Clair–Lake Erie system is 11,703 MTA. Thus, overall, in-lake processes account for about a quarter of the total (external plus internal) TP input. The internal input is not evenly distributed among the system's basins, however, with Lake St. Clair and Lake Erie's western, central, and eastern basins receiving 6, 13, 21 and 60% of the total internal P input, respectively. Our results highlight the importance of accounting for the internal P loading in nutrient cycling modeling and load reduction strategies for large lake systems. [Display omitted] • Net phosphorus (P) output from Lake Erie substantially exceeds external inputs. • Internal P inputs represent about a quarter of Lake Erie's total P input. • Internal inputs include sediment efflux, shoreline erosion and sediment resuspension. • Internal P loading may contribute to the re-eutrophication of Lake Erie. [ABSTRACT FROM AUTHOR]

Groundwater potential mapping and its sustainable development are an important aspect in Leh valley due to an increase of tourists and the local population. In the present study, the groundwater potential zones were delineated by adopting a frequency ratio (FR) model. Land use and land cover, hydro geomorphology, slope, geology, lineament density, drainage density, spring well locations and ground water level were the thematic factors considered for groundwater potential zone mapping. There are 86 spring wells located in the study area, of which 60 wells were considered for success rate and remaining 26 wells considered for prediction rate in the FR model. The final groundwater potential map was classified into five zones as very high, high, moderate, low, and very low. The success and prediction rates of FR model were measured as 81.25% and 77.23% respectively. Water budget of the valley was also calculated on the basis of consumption, demand and supply of water by taking account of the floating population. There is a huge demand of water supply requirement during the tourist season from May to September months and deficiency of water in the area was calculated as 4,224,557 (in l). Finally, suitable sites for artificial recharge for sustainable groundwater management were identified. The sites were selected on the basis of depth of groundwater level, source of spring well locations and gradient from natural spring to selected recharge wells. [ABSTRACT FROM AUTHOR]

This study evaluates the alternative conceptual models for groundwater modelling. A true model was created with a synthetic alluvial fan-plain hydrogeological framework. Various alternative conceptual models were evaluated for groundwater flow simulations. The first alternative model is a single aquifer layer model; the second alternative model is a 3-layer aquifer model; and the third model is a 5-layer model consisting of 3 aquifers separated by 2 aquitards. All models could fit very well to the observations with optimized values of hydraulic conductivities. However, the single aquifer layer model can only compute water balance components with good accuracy. The 3-layer aquifer model can be used for water balance computation and groundwater head simulation with small errors. The 5-layer model is capable of simulating water budget, groundwater head distribution and travel times with high accuracy. Multi-model analysis found only the 3rd alternative model superior. [ABSTRACT FROM AUTHOR]

A 3D coupled physical-biogeochemical model is developed and applied to Bizerte Lagoon (Tunisia), in order to understand and quantitatively assess its hydrobiological functioning and nutrients budget. The biogeochemical module accounts for nitrogen and phosphorus and includes the water column and upper sediment layer. The simulations showed that water circulation and the seasonal patterns of nutrients, phytoplankton and dissolved oxygen were satisfactorily reproduced. Model results indicate that water circulation in the lagoon is driven mainly by tide and wind. Plankton primary production is co-limited by phosphorus and nitrogen, and is highest in the inner part of the lagoon, due to the combined effects of high water residence time and high nutrient inputs from the boundary. However, a sensitivity analysis highlights the importance of exchanges with the Mediterranean Sea in maintaining a high level of productivity. Intensive use of fertilizers in the catchment area has a significant effect on phytoplankton biomass increase. [ABSTRACT FROM AUTHOR]

The sustainability of urban water systems is often compared in small numbers of cases selected as much for their familiarity as for their similarities and differences. Few studies examine large urban datasets to conduct comparisons that identify unexpected similarities and differences among urban water systems and problems. This research analyzed a dataset of 142 cities that includes annual per capita water use (m 3 /yr/cap) and population. It added a 0.5 ° grid annual water budget value (P-PET/yr) as an index of hydroclimatic water supply. With these indices of urban water supply and demand, we conducted a hierarchical cluster analysis to identify relative similarities among, and distances between, the 142 cases. While some expected groupings of climatically similar cities were identified, unexpected clusters were also identified, e.g., cities that use water at greater rates than local climatic water budgets provide. Those cities must seek water from greater distances and greater depths. They face greater water and wastewater treatment costs. To become more sustainable they must increase water use efficiency, demand management, reuse, and recycling. The significance of the population variable suggests that adding other explanatory socio-economic variables, as well as more precise water system indices, are logical next steps for comparative analysis of urban water sustainability. [ABSTRACT FROM AUTHOR]

The US Army is concerned about the multiple critical-resource issues faced by its installations, with water being key among these resources. Adverse water issues include limited supply, rising cost, and impaired quality; strategies are needed to mitigate these undesirable effects. A major obstacle to developing strategies is the lack of detailed information about how Army facilities use water because on Army installations, water use is typically metered at the aggregate level rather than by area, function, or individual building. New research projects are focused on developing methods and models to disaggregate site-level monthly water meter data and identify classes of facilities on the basis of function, equipment, and schedules of use. Draft methods were tested using information obtained from an installation water audit at Fort Leonard Wood, Mo. The outcomes of these models will help inform future conservation strategies as Army installations seek to reduce utility costs. [ABSTRACT FROM AUTHOR]

Historically, the building industry has taken a somewhat compartmentalized approach to water management. The use of alternative water sources (e.g., rainwater, municipal reclaimed water, air conditioning condensate, or stormwater) or the reuse of wastewater (gray or black) significantly complicates the water budget picture. A total water management systems approach, taking into consideration water from various sources, both inside and outside the building, should be implemented in order to devise a strategy for optimal reduction of potable water consumption and wastewater generation. A building water cycle is complicated by nonlinearity introduced by water recycling, necessitating prioritization. A prioritization framework for the support of integrated building water management (IBWM) is presented. The framework is developed by prioritizing both water demands and supplies, recognizing that there are tradeoffs among water usage, energy requirements, and costs based on changes in water quality. The resulting algorithm successfully produces dynamic output water profiles based on three scenarios (constant, residential, and commercial) utilizing the prioritization framework. The ability of the algorithm to track water allocation and potable water reduction is tested using scenarios applied to a hotel building water cycle. Evaluation of multiple water demands and sources at varying temporal scales validates the framework's flexibility. [ABSTRACT FROM AUTHOR]

Reliable estimates of evaporative water loss are required to assess the urban water budget in support of division of water resources among various needs, including heat mitigation measures in cities relying on evaporative cooling. We report on urban evaporative water loss from Arnhem and Rotterdam in the Netherlands, using eddy covariance, scintillometer and sapflow observations. Evaporation is assessed at daily to seasonal and annual timescale. For the summer half-year (April–September), observations from Arnhem and Rotterdam are consistent regarding magnitude and variability of evaporation that typically varies between 0.5 and 1.0 mm of evaporation per day. The mean daily evaporative cooling rate was 20–25 Wm −2 , 11–14% of the average incoming solar radiation. Evaporation by trees related to sapflow was found to be a small term on the water budget at the city or neighbourhood scale. However, locally the contribution may be significant, given observed maxima of daily sap flows up to 170 l per tree. In Arnhem, evaporation is strongly linked with precipitation, possibly owing to building style. During the summer season, 60% of the precipitation evaporated again. In Rotterdam, the link between evaporation and precipitation is much weaker. An analysis of meteorological observations shows that estimation of urban evaporation from routine weather data using the concept of reference evaporation would be a particularly challenging task. City-scale evaporation may not scale with reference evaporation and the urban fabric results in strong microweather variability. Observations like the ones presented here can be used to evaluate and improve methods for routine urban evaporation estimates. [ABSTRACT FROM AUTHOR]

The United Nations Sustainable Development Goal (SDG) ensures adequately accessible water and management for all. Due to the rapid increase in population and industries along the Ganga river, it is necessary to estimate the water budget to fulfill the demand for water in the future. The Mann-Kendall (MK) test conducted on the Noah-Land Surface Model data for 72 years results in a maximum declining trend of water budget in the Yamuna Lower (Q = −3.82 BCM/year), and a minimum in the Damodar sub-basin (Q = −0.10 BCM/year). All the sub-basins show an increase in groundwater level (mbgl) except the Kali Sindh, which shows a decreasing trend (Q = −0.07 m/year). The percentage change was also estimated in all the sub-basins, including various parameters such as precipitation, evapotranspiration, runoff, water budget, and temperature. The extremely severe groundwater drought was estimated using the Standard Groundwater Level Index (SGWLI), from which the values for the Ram Ganga Confluence (SGWLI = 2.44; 2005), Upper stream of Gomti (SGWLI = 2.06; 2014), Ghaghra (SGWLI = 2.22; 2005), Ram Ganga (SGWLI = 2.28; 2005), Yamuna Lower (SGWLI = 2.13; 2007), Kali Sindh (SGWLI = 2.30,2.67; 2002, 2003), Chambal Upper (SGWLI = 2.30,2.20; 2001, 2003), Son (SGWLI = 2.02; 2010), Gandak (SGWLI = 2.37; 2010), Kosi (SGWLI = 2.08; 2012), Damodar (SGWLI = 2.72; 2010), and Bhagirathi (SGWLI = 2.06; 2014) were obtained for a total of 62,050 observed well data.The obtained in-situ point data is converted into the surface raster using a geostatistical technique. Our results show a declining trend in the water budget of all the 19 sub-basins of the Ganga basin and also the groundwater drought in several parts. [ABSTRACT FROM AUTHOR]

Monthly and annual water and phosphorus mass budgets were set up over the year 2010 for the Lake Rio Verde, Brazil. Limited data for the water budget was compensated using an interpolation method with data water budget data of a nearby reservoir. Thus, errors of ca. 1.5% were estimated for the water budgets. Dominant P mass input terms were inflows from the rivers and direct run off into the reservoir. Main output terms were P outflow via rivers and industrial water abstraction. Equalizing the P inputs and outputs leads to a sediment phosphorus uptake term were estimated at 35% of the annual P inflow, but with a possible weak correlation between monthly P sediment/water exchange and monthly precipitation figures. Sediment characteristics likely play an important role in the P sediment-water exchange. High concentrations of P in sediment pore water, and seasonal reductions in the oxidized surface layer of sediment suggests reduction of the potential of the sediment to retain P under current and likely, increased, P loads to the reservoir. Future management of the reservoir, therefore, requires continued monitoring and catchment management to mitigate nutrient both point source and diffuse loads. This necessitates an integrated approach to reduce pressures on the reservoir. Failure to address potential problems can lead to reduced water quality, with associated increased treatment costs for water supply. [ABSTRACT FROM AUTHOR]

this study was aimed to assess the causes of the structural decline in the renewal rate of a pristine oak forest close to Rome (central Italy) by analyzing long-term measurements of the water budget in open and fenced areas. Despite dry climate conditions in the area, long-term soil moisture measurements at 100 cm soil depth indicated that an enough large amount of water is available to oaks during the whole year. Moreover, while trees did not suffer from water deficit during summer, they may experience root asphyxia during rainy years. The analysis of the water budget clarified that, even during exceptionally-dry years, oak renewal was not limited by dry climate conditions. Instead, overgrazing due to the high demographic pressure determined by wild boars which eat almost exclusively oak acorns and deer which eat the leafs of young plants was one of the most important factors affecting oak renewal. [ABSTRACT FROM AUTHOR]

This study comparatively evaluates the Hydrological Simulation Program-FORTRAN (HSPF) model and the Canadian ArcView Nutrient and Water Evaluation Tool (CANWET) for non-point source pollution (NPS) management in rural Ontario watersheds. Both models were calibrated, validated, and applied to a 52 km² headwater rural watershed known as the Canagagigue Creek near Elmira in the Grand River basin, Ontario, Canada. A comparison of the simulated and observed values for stream flow, surface runoff, subsurface runoff, evapotranspiration, and sediment yield showed that (Better Assessment Science Integrating Point and Nonpoint Sources) BASINS/HSPF and CANWET models have similar capabilities to simulate various hydrological processes at the watershed scale. The seasonal stream flow comparison between observed and simulated values from HSPF and CANWET showed Nash-Sutcliffe efficiency (Nash-E) coefficients of 0.80 and 0.72, respectively. The monthly comparison between the simulated and observed stream flow yielded Nash-E coefficients of 0.88 and 0.94 for HSPF and CANWET, respectively. Overall, both models predicted the components of the annual, seasonal, and monthly water budget accurately. There was a considerable difference in the monthly simulated sediment yield by both models. This difference is consistent with the surface runoff variation predicted by both models. Both models predicted sediment yield with early winter and spring storms which is typical for southern Ontario. [ABSTRACT FROM AUTHOR]

The scarcity of water available for landscape irrigation is a great challenge facing urban greenery and landscaping initiatives in arid and semi-arid regions. The Imam Abdulrahman bin Faisal University (IAU) has established a new campus on 3,2000,000 M2 of land extended to the eastern coast of the Arabian Gulf. Since moving to the Eastern Campus in 2014, the IAU has been working hard to increase the green spaces to minimize the environmental impact of harsh climate, hard surfaces, and building masses. In its endeavor to achieve this goal, the management of landscape plant materials and irrigation systems has not kept pace with the development of the campus. Almost 800 M3/day of irrigation water has been pumped into the system however it fails to maintain good quality landscape plants. As a result, green spaces suffer great degradation especially during hot months due to insufficient irrigation management and other factors. This study is an attempt to explore the relationship between the expansion of green spaces on the IAU's Eastern Campus and their irrigation requirements. It applied the investigative analytical method to study and analyze the green spaces elements and their daily water budget, which led to the proposal of a synchronous management approach balancing the amount of water available for irrigation purposes and the qualities and expansion of landscape plant materials. The study found that applying the required water budget to plants since their establishment on their permanent locations is a waste of available resources, but it must be gradually increased based on the plant's size, its growth rate, and seasonal changes. However, a synchronous management approach is required to ensure that good quality landscapes are maintained while using limited available resources. [ABSTRACT FROM AUTHOR]

Abstract: We carried out an eco-hydrological analysis to evaluate the most important effects of land use changes on the hydrological functioning of a fen system in Poland. We measured water levels (hydraulic heads) and water flow along a transect through the study area and also analysed land use changes using historical maps. Major hydrological changes occurred after c. 1950 when a dense drainage network was constructed and in the last decade when large fishponds were built. Nowadays, water levels in most of the fens and fen meadows are too low and the fluctuations too large for a long-term preservation of fen ecosystems. The mean water tables range from 0.3 to 0.8m below soil surface with fluctuations from 0.7 up to 1.5m. A second important cause of the hydrological changes of the system was the afforestation of the adjacent infiltration areas leading to increased evapotranspiration and a decreased groundwater flow to the wetlands. Finally, a recent increase in groundwater abstraction for agricultural purposes has probably lowered the groundwater even further. We conclude that a full restoration of the fen is not possible under the present conditions. An alternative restoration goal could be conservation and restoration of species-rich fen meadows, but also then improving the hydrological conditions will be necessary. While the focus is often on the local factors influencing the restoration prospects of a fen system, the regional processes are at least equally important. In this paper we discuss an importance of both local and regional factors. [ABSTRACT FROM AUTHOR]

We developed a water budget runoff model for the Salt and Verde River basins of central Arizona and used the outputs of 6 global climate models (GCMs) to estimate runoff in the future under assorted emissions scenarios developed by the Intergovernmental Panel on Climate Change (IPCC). We used a statistical downscaling routine to refine the GCM outputs for the 2 basins, and we found that all model-scenario combinations simulate a mean temperature rise in the study area of between 2.4 and 5.6°C, using year 2050 greenhouse gas concentrations. Mean changes in precipitation vary substantially among the models and scenarios, and, as a result, changes in runoff vary from 50 to 127% of historical levels. Assuming equal probabilities associated with each scenario and model run, the overall results suggest that runoff from the Salt and Verde will have an approximately 85% chance of being less strong, the certainty of which is related to consensus on warming in the study area. The large variability among predictions of precipitation trends introduces substantial uncertainty. [ABSTRACT FROM AUTHOR]

The paper presents the Black Sea morphometry and hydrographic characteristics, its network of tributaries and the fresh water supply. The published and directly measured by the author data from Sulina and Constanta gauges (situated on Romanian shore), as well as from stations in Bulgaria, Ukraine, Russia and Georgia have been used for analysing the sea level variations. The time series taken into consideration cover the period from 1858 to 1998. The water budget of the Black Sea and the sea level variations at different coastal zones have been analysed for highlighting the influence of the river - sea interactions. The Danube River water supply has an important influence on the sea level fluctuations. A trend of the sea level variations in time for different coastal zones was evidenced. Considerations on eustatic and subsidence processes along the Black Sea coasts are given. [ABSTRACT FROM AUTHOR]

Abstract: Water scarcity in North Cyprus (NC) began in the 1960s and is still tremendously increasing. Thus far no serious measurements have been taken to address this problem. Increased water demands led to extraction of water from unrestricted groundwater resources. Extreme water extractions caused the salinization of coastal aquifers up to brackish waters and the consequent depletion of interior aquifers. Such a situation requires precise control of water resources through an integrated water resources management (IWRM). Although the situation has reached an alarming state, no detailed research has been performed to establish the present demands of water in order to anticipate the future demands. Hence, this study, based on the IWRM approach, examines water budget of the country. [Copyright &y& Elsevier]

Tools initially developed (or analyzing climate or the environment are often used subsequently by scientists in more applied areas of research. The Thornthwaite-Mather (T-M) water budget equation was primarily developed to calculate a water budget, which, of course, had obvious uses for irrigation purposes. But John Russell Mather hoped his work would be used in a variety of applications, and fortunately he lived to see it used even by his son in the arena of vector-borne diseases. Our team is screening various climatic and environmental variables to identify relevant determinants of tick abundance in an effort to predict levels of disease risk both spatially and temporally in the northeastern United States. Identifying relevant climatic and environmental variables delimiting tick habitat at a high resolution has led us to consider a variety of tools designed for environmental applications. We used the Thornthwaite-Mather water budget technique to predict soil moisture under forest canopies, the primary habitat for the tick vectors of Lyme disease bacteria. To date, the exact controls of spatio-temporal tick distribution are not yet confirmed, but we now believe that whichever variables are shown to most precisely delimit the extent of tick distributions over large areas can be identified by vegetation and other moisture-based variables using satellite sensor data. [ABSTRACT FROM AUTHOR]

Biogeographers and ecologists often need to quantify species-environment relationships to understand the distribution of vegetation, and to assess changes in patterns resulting from environmental change. A water budget approach, which incorporates evaporative demand and moisture availability, is compared to traditional climatic variables in terms of ability to predict species growth and abundance in eastern North America. Firstly, tree growth is examined using tree-ring chronologies obtained from the International Tree-Ring Data Bank, correlated with climatic data from the nearest site in the US Historical Climatology Network. Secondly, logistic regression is used to model the range of American beech (Fagus grandifolia) using pollen records from the World Data Center for Paleoclimatology, and climatic data from NCAR's Community Climate Model (CCM1) general circulation model (GCM) for the control, 6 ka, and 11 ka runs. Tree growth, especially for oaks and other deciduous trees, correlates more strongly with early growing-season deficit than with precipitation. Water budget variables (actual evapotranspiration and deficit) are also more effective than traditional climatic variables in modeling the range of beech. A water budget approach is attractive for modeling vegetation dynamics because it transcends geographic scale; it is able to model both local and continental-scale phenomena. [ABSTRACT FROM AUTHOR]

An analysis of Lake Superior water levels from 1948-1999 reveals that the seasonal cycle has decreased in amplitude by 20% (from 40 cm to 32 cm). This change is manifested as a downward trend in summer and autumn lake levels (when levels are typically highest) accompanied by roughly no change in winter and spring lake levels (and an overall 4-cm drop in annual mean levels). The decreased rates of seasonal rise and fall in lake level over the 51-year interval reflect a large decrease in the net monthly influx of water during the late spring (up to -1,360 m³/s) coupled with a nearly compensating increase in net influx during late autumn (up to +1,100 m³/s). Analysis of the Lake Superior water budget indicates that these changes are primarily the result of trends in runoff and over-lake precipitation. A systematic decrease in outflow through the St. Marys River is also evident during July-December (in association with the lower lake levels), as well as a moderate shift in the seasonal pattern of lake evaporation (but not the annual mean). The observed water budget trends are primarily related to variations in climate, rather than lake regulation. Land surface effects are also important, as suggested by a 20% increase in annual mean evapotranspiration during the 51-year interval and large changes in monthly storage (e.g., snowmelt, groundwater, etc.). Significant uncertainties are present in the calculated water budget, and it is suggested that a likely source of error is in measured precipitation and (especially) runoff. [ABSTRACT FROM AUTHOR]

Holocene lake level history and paleogeography of Lake Erie are re-interpreted with the aid of new bathymetry, existing water budget data, and published information. Morphology and elevation of present and former shoreline features (sand ridges, forelands, spits, bars, and fans) record the water level at which they were formed. Of eighteen such features observed in Lake Erie, six occur nearshore and were formed at or near present lake level, and twelve features apparently formed at lower lake levels. It seems likely that lake level fell below the level of the outlet sill during the 9-6 ka climate optimum, when warmer and drier conditions prevailed. During such times lake level likely rose and fell as controlled by the water budget, within a window of constraint imposed by increases and decreases in evaporation, which would have varied directly with lake surface area. Near Buffalo, possible shoreline features occurring 3-6 km offshore at depths of 9-12 m could have formed at lower lake levels. Annual water volumes in each term of the water budget, (runoff, precipitation, and evaporation) are large relative to the volumetric capacity of Lake Erie itself Such events as introduction of even a modest amount of upper Great Lakes water, or the onset of cooler and less dry climate conditions, could cause significant, rapid, lake level rise. Schematic reconstructions illustrate changing paleogeography and a Holocene lake level history which has varied with: blocking/unblocking of outlet sills; erosion of outlet sills; distance from outlet sills; differential isostatic rebound; upper Great Lakes drainage flowing into or bypassing the lake; and climate-driven water budget of the Lake Erie drainage basin. [ABSTRACT FROM AUTHOR]

Dew can represent an alternate water source in epiphytic bromeliads. However, the physiological relevance of dew to withstand the dry season, within seasonal forests, is not fully understood. To study the effect of dew deposition in the physiological response of four Tillandsia species with contrasting morphologies, we performed an experiment in the tropical dry deciduous forest of Dzibilchaltún, Mexico, during the transition from the wet to the dry season. Half of the individuals were covered every night with a plastic tarp to prevent dew deposition. Environmental variables were monitored, and physiological variables (relative water content, leaf succulence, nocturnal tissue acidification and electron transport rate) were measured at the beginning and end of the experiment. We found that throughout the drought, there was consistent nighttime dew formation for >4 h. Both the time the leaves spent at a temperature below dew point of the air and the effect on water and carbon metabolism was species -specific, as evidenced by the comparison among the exposed and covered (dew -deprived) plants. Tillandsia elongata and Tillandsia brachycaulos had longer times of dew formation and showed higher water content at the end of the experiment when exposed to dew, the latter species also had a significant effect of dew on nocturnal acidity. In contrast, neither Tillandsia yucatana nor Tillandsia fasciculata seemed to be using dew as a relevant source of water during the dry period. We discuss the species' morphoanatomical traits that may be related to the differences in dew formation and use. [ABSTRACT FROM AUTHOR]

Dew can represent an alternate water source in epiphytic bromeliads. However, the physiological relevance of dew to withstand the dry season, within seasonal forests, is not fully understood. To study the effect of dew deposition in the physiological response of four Tillandsia species with contrasting morphologies, we performed an experiment in the tropical dry deciduous forest of Dzibilchaltún, Mexico, during the transition from the wet to the dry season. Half of the individuals were covered every night with a plastic tarp to prevent dew deposition. Environmental variables were monitored, and physiological variables (relative water content, leaf succulence, nocturnal tissue acidification and electron transport rate) were measured at the beginning and end of the experiment. We found that throughout the drought, there was consistent nighttime dew formation for >4 h. Both the time the leaves spent at a temperature below dew point of the air and the effect on water and carbon metabolism was species -specific, as evidenced by the comparison among the exposed and covered (dew -deprived) plants. Tillandsia elongata and Tillandsia brachycaulos had longer times of dew formation and showed higher water content at the end of the experiment when exposed to dew, the latter species also had a significant effect of dew on nocturnal acidity. In contrast, neither Tillandsia yucatana nor Tillandsia fasciculata seemed to be using dew as a relevant source of water during the dry period. We discuss the species' morphoanatomical traits that may be related to the differences in dew formation and use. [ABSTRACT FROM AUTHOR]

The purpose of this study was to identify those water budget components of the Great Lakes that have most frequently been a major cause of anomalous net basin supplies (NBS) and of rising and falling lake levels at the monthly time scale. Principal component analysis and a simple counting of relative frequencies revealed that on the upper lakes NBS anomalies are most sensitive to over-lake precipitation, but on the lower lakes they are most sensitive to runoff. This shift is due to a downstream increase in the magnitude and variability of runoff. Evaporation variability plays a larger role in the NBS of the upperthan the lower lakes and is most important during dry months. Duringwet months evaporation is not as much suppressed as one might assumefrom the simple cloud cover/insolation/temperature/evaporation relationship; this is most likely due to an increase in wind speed. High and rising as well as low and falling lake levels are the result of anomalous NBS on all lakes and represent condition beyond the capabilities of lake-level regulations. Changing conditions--low but rising levels or high but falling levels--are the result of anomalous NBS for all of the lakes except Ontario, for which almost all such changes are achieved by regulating the outflow. [ABSTRACT FROM AUTHOR]