Water Storage Volume Research Articles

Life-cycle savings for a flat-plate solar water collector plant in Chile

In Chile, flate-plate solar water collector (FPSWC) plants have not yet been sufficiently developed despite the excellent solar conditions of the country's territory. Two of the main parameters affecting the behavior of these plants are the collection area and the water storage volume. In this paper, an energy performance model of an FPSWC plant is used along with genetic algorithms (GAs) to optimize the combination of these two parameters in order to produce the maximum life-cycle savings (LCS). This model is applied to 182 locations in Chile and 6 consumption profiles with the purpose of creating a solar map for this kind of plant throughout the country. The financial results show that the installation of an optimized FPSWC plant is convenient in all the analyzed locations. Furthermore, results are noteworthy in the northern zone of Chile with respect to the others due to excellent meteorological conditions. A sensitivity analysis was carried out at the locations with higher and lower LCS, showing that consumption temperature mainly affects zones with higher radiation. This study allows us to provide evidence that the utilization of FPSWC plants should be promoted in order to induce rapid growth and development of this important technology in Chile.

Sanitary evaluation of domestic water supply facilities with storage tanks and detection of Aeromonas, enteric and related bacteria in domestic water facilities in Okinawa Prefecture of Japan

To provide for temporary restrictions of the public water supply system, storage tanks are commonly installed in the domestic water systems of houses and apartment buildings in Okinawa Prefecture of Japan. To learn more about the sanitary condition and management of these water supply facilities with storage tanks (hereafter called “storage tank water systems”) and the extent of bacterial contamination of water from these facilities, we investigated their usage and the existence of Aeromonas, enteric and related bacteria.Verbal interviews concerning the use and management of the storage tank water systems were carried out in each randomly sampled household. A total of 54 water samples were collected for bacteriological and physicochemical examinations. Conventional methods were used for total viable count, fecal coliforms, identification of bacteria such as Aeromonas, Enterobacteriaceae and non-fermentative Gram-negative rods (NF-GNR), and measurement of residual chlorine. On Aeromonas species, tests for putative virulence factor and an identification using 16S rRNA and rpoB genes were also performed.Water from the water storage systems was reported to be consumed directly without boiling in 22 of the 54 houses (40.7%). 31 of the sampled houses had installed water storage tanks of more than 1 cubic meter (m3) per inhabitant, and in 21 of the sampled houses, the tank had never been cleaned. In all samples, the total viable count and fecal coliforms did not exceed quality levels prescribed by Japanese waterworks law. Although the quantity of bacteria detected was not high, 23 NF-GNR, 14 Enterobacteriaceae and 5 Aeromonas were isolated in 42.6%, 7.4% and 3.7% of samples respectively. One isolated A. hydrophila and four A. caviae possessed various putative virulence factors, especially A. hydrophila which had diverse putative pathogenic genes such as aer, hlyA, act, alt, ast, ser, and dam. Many bacteria were isolated when the concentration of residual chlorine was below 0.1 mg/l and the water temperature was above 20 °C. These results suggest that elevated water temperature and mismatch between tank size and water demand lead to loss of residual chlorine in tap water. Therefore, to minimize growth of aquatic bacteria such as Aeromonas spp. and Pseudomonas spp., we recommend that an appropriate size tank and/or volume of stored water is always used, and also suggest installation of some means of reducing water temperature such as shading.

KAJIAN KEBERLANJUTAN ALIRAN DASAR SUNGAI MELALUI ANALISIS KURVA RESESI HIDROGRAF PADA DAS KEDUANG KABUPATEN WONOGIRI PROVINSI JAWA TENGAH

The streamflow hydrograph recession curve notes that behavior of the relationship between the aquifer structure and dependencies with the groundwater outflow towards river basin channel. The recession behavior of river basin hydrographs will investigate to understand the hydrology processes of the river basin in the future. This research was conducted with the aim: to analyze the characteristics of the baseflow recession based on the parameters and coefficients of the recession, and the shape of the individual recession curve and the master recession curves both manually and through the processing of genetic algorithms using a linear reservoir model of hydrooffice software package recession curve (RC) 4.0.
 The results of the visualization of the recession curve shape of the watershed of the research shows there is a very interesting trend in the watershed storage process.The characteristics of the baseflow recession to research watershed with the recession curve slope describe the baseflow recession conditions, especially excellent water storage. The river basin of Keduang have the form of a relatively sloping recession curves, both individual and master recession curve with relatively high recession constant ranged between 0,80 – 0,90 have baseflow recession characteristic is excellent, i.e. the watershed water storage which is the higher volume of water storage.

Including hydrological self-regulating processes in peatland models: Effects on peatmoss drought projections.

The water content of the topsoil is one of the key factors controlling biogeochemical processes, greenhouse gas emissions and biosphere - atmosphere interactions in many ecosystems, particularly in northern peatlands. In these wetland ecosystems, the water content of the photosynthetic active peatmoss layer is crucial for ecosystem functioning and carbon sequestration, and is sensitive to future shifts in rainfall and drought characteristics. Current peatland models differ in the degree in which hydrological feedbacks are included, but how this affects peatmoss drought projections is unknown. The aim of this paper was to systematically test whether the level of hydrological detail in models could bias projections of water content and drought stress for peatmoss in northern peatlands using downscaled projections for rainfall and potential evapotranspiration in the current (1991-2020) and future climate (2061-2090). We considered four model variants that either include or exclude moss (rain)water storage and peat volume change, as these are two central processes in the hydrological self-regulation of peatmoss carpets. Model performance was validated using field data of a peatland in northern Sweden. Including moss water storage as well as peat volume change resulted in a significant improvement of model performance, despite the extra parameters added. The best performance was achieved if both processes were included. Including moss water storage and peat volume change consistently reduced projected peatmoss drought frequency with >50%, relative to the model excluding both processes. Projected peatmoss drought frequency in the growing season was 17% smaller under future climate than current climate, but was unaffected by including the hydrological self-regulating processes. Our results suggest that ignoring these two fine-scale processes important in hydrological self-regulation of northern peatlands will have large consequences for projected climate change impact on ecosystem processes related to topsoil water content, such as greenhouse gas emissions.

Aplicação de um protocolo de avaliação ambiental rápida em dois reservatórios do semiárido brasileiro

In the semi-arid region of Brazil, artificial reservoirs are ecosystems of extremely important ecological and social. Due to pressures caused by long periods of pluviometric irregularity, the reservoirs Cachoeira I and Barra, located in the interior of Pernambuco, have been subject to very significant changes, marked mainly by the reduction of stored water volume, seasonal changes in the abiotic parameters, reduction of riparian vegetation and absence of macrophytes. All these changes were observed in this study through the use of an auxiliary monitoring tool, a rapid assessment protocol adapted for lentic ecosystems of semiarid, capable of detecting numerous types of environmental changes, assisting in monitoring these springs.

Vertical surface water–groundwater exchange processes within a headwater floodplain induced by experimental floods

AbstractRestoring hydrologic connectivity between channels and floodplains is common practice in stream and river restoration. Floodplain hydrology and hydrogeology impact stream hydraulics, ecology, biogeochemical processing, and pollutant removal, yet rigorous field evaluations of surface water–groundwater exchange within floodplains during overbank floods are rare. We conducted five sets of experimental floods to mimic floodplain reconnection by pumping stream water onto an existing floodplain swale. Floods were conducted throughout the year to capture seasonal variation and each involved two replicate floods on successive days to test the effect of varying antecedent moisture. Water levels and specific conductance were measured in surface water, soil, and groundwater within the floodplain, along with surface flow into and out of the floodplain. Vegetation density varied seasonally and controlled the volume of surface water storage on the floodplain. By contrast, antecedent moisture conditions controlled storage of water in floodplain soils, with drier antecedent moisture conditions leading to increased subsurface storage and slower flood wave propagation across the floodplain surface. The site experienced spatial heterogeneity in vertical connectivity between surface water and groundwater across the floodplain surface, where propagation of hydrostatic pressure, preferential flow, and bulk Darcy flow were all mechanisms that may have occurred during the five floods. Vertical connectivity also increased with time, suggesting higher frequency of floodplain inundation may increase surface water–groundwater exchange across the floodplain surface. Understanding the variability of floodplain impacts on water quality noted in the literature likely requires better accounting for seasonal variations in floodplain vegetation and antecedent moisture as well as heterogeneous exchange flow mechanisms. Copyright © 2016 John Wiley & Sons, Ltd.

The Influence of Environmental Constraints on the Water Value

The establishment of more severe hydrological environmental constraints, usually as seasonal minimum flows (ϕ) and maximum ramping rates (ρ), on hydropower operation is a growing trend. This paper presents a study on the influence of ϕ and ρ on the water values (WV) of a real hydropower plant that participates in the Spanish day-ahead electricity market. For this purpose, a master-slave algorithm, based on stochastic dynamic programming (SDP) and deterministic mixed integer linear programming (DMILP), is used on a real hydropower plant. The master module, based on SDP, has a yearly planning period with weekly time steps and considers three state variables: stored water volume in the reservoir at the beginning of each week; weekly water inflow; and average weekly energy price. The slave module, based on DMILP, has a weekly planning period with hourly time steps and considers many features of the hydropower plant operation, such as: start-up costs, evaporation, wear and tear costs, etc. The results indicate that WV of a hydropower plant are very sensitive to the presence of these constraints; ϕ especially during the wettest season and ρ during the driest one. As the severity of ϕ and ρ increase, WV increase and decrease, respectively.

Calling site selection by the bromeliad-dwelling treefrog Phyllodytes melanomystax (Amphibia: Anura: Hylidae) in a coastal sand dune habitat

ABSTRACTWe studied bromeliad selection by calling males of Phyllodytes melanomystax. The study site was a restinga environment in the northeastern state of Bahia, northeastern Brazil. We sampled 202 bromeliads, 101 with and 101 without calling males. We used multiple logistic regression analysis and Wald test to identify which of nine environmental variables investigated could explain the occurrence of calling males within bromeliads. The presence/absence of calling males in bromeliads was influenced by the number of bromeliads in a 2 m radius and the amount of debris inside the rosettes, while physical variables of bromeliads and the volume of stored water inside their rosettes had no influence. The mark-recapture procedure of P. melanomystax revealed site fidelity. This study is the first to explain the pattern of bromeliad selection by a species of the bromeliad-dwelling frog genus Phyllodytes.

Assessing floodplain porosity for accurate quantification of water retention capacity of near-natural riparian ecosystems—A case study of the Lower Biebrza Basin, Poland

Near-natural lowland floodplains, which nearly disappeared in temperate climates due to the vast anthropopression, play a critically important role in shaping biodiversity in regional scales. The other important aspects of floodplains such as their role in flood mitigation for downstream reaches of rivers, catchment-scale ecosystem services, and agriculture emphasize the need for research of these ecosystems, with special focus on the flood-vegetation interactions. In our study we performed an experiment oriented at the accurate quantification of water retention capacity of the densely vegetated floodplain located in NE Poland, referring to the floodplain porosity (ε). We conducted measurements of the geometry of selected types of the floodplain vegetation, with a special focus on the communities dominated by the common reed (Phragmites australis (Cav.) Trin. ex Steud.), the reed-manna grass (Glyceria maxima (Hartm.) Holumb.) and dominant representatives of loosely structured sedges (Carex acuta L.) and of tussock sedges (Carex appropinquata Schumach.)., which allowed us to derive the volume of these species and eventually the floodplain porosity coefficients in a function of various flood depths. Estimated values of ε equalled from 0.882 to 0.993. Average value of ε for all vegetation communities analysed for all flood depths considered equalled 0.968. Consideration of the derived ε values in the case study on the floodplain water retention capacity estimation in hypothetical conditions of a standard flood (2-year recurrence interval) resulted in the reduction of the total water storage volume of the floodplain by 0.75mnm3 of water. Results of our research indicated that the studies oriented at quantification of water storage within the floodplain as an asset for ecosystem services should consider floodplain porosity due to its significance in the accurate estimation of floodplain capacity.

Assessing Climate Impacts on Hydropower Production: The Case of the Toce River Basin

The aim of the presented study is to assess the impacts of climate change on hydropower production of the Toce Alpine river basin in Italy. For the meteorological forcing of future scenarios, time series were generated by applying a quantile-based error-correction approach to downscale simulations from two regional climate models to point scale. Beside a general temperature increase, climate models simulate an increase of mean annual precipitation distributed over spring, autumn and winter, and a significant decrease in summer. A model of the hydropower system was driven by discharge time series for future scenarios, simulated with a spatially distributed hydrological model, with the simulation goal of defining the reservoirs management rule that maximizes the economic value of the hydropower production. The assessment of hydropower production for future climate till 2050 respect to current climate (2001–2010) showed an increase of production in autumn, winter and spring, and a reduction in June and July. Significant change in the reservoir management policy is expected due to anticipation of the date when the maximum volume of stored water has to be reached and an increase of the reservoir drawdown during August and September to prepare storage capacity for autumn inflows.

Experimental study of the solar photovoltaic contribution for the domestic hot water production with heat pumps in dwellings

The present paper describes experimental work, carried out during an entire year on a heat pump used for domestic hot water (DHW) production, which is powered from photovoltaic panels and the grid simultaneously. The system was designed and controlled to give priority to the renewable source to reach the maximum solar contribution.The aim of the study was to analyze the real possibilities of using photovoltaic energy to produce DHW with heat pumps in dwellings. The system developed (heat pump + PV) works without batteries and therefore the energy storage is carried out by the hot water accumulated in the tank.The design of the system was carried out in order to optimize the solar contribution. Some key aspects of the design are: the heat pumps' power, the water storage volume, the control strategy and a device to derive the excess of PV electricity to a secondary heater.The system was tested for typical DHW production of a typical family of 4 residence: 130 liters at 55°C, about 6.2 kWh a day. Tests were carried out in the university laboratory located in Alicante (Spain). The results during a year of study demonstrates that the annual average efficiency of the heat pump (SPFHP) could be close to 3.5 and the annual average efficiency of the whole system would be near 9, while the solar contribution would be higher than 60%.

Optimizing Hydrothermal Scheduling with Non-Convex Irrigation Constraints: Case on the Chilean Electricity System

Water stored in large reservoirs can support various economic activities, such as electricity generation and agriculture, that need to be efficiently coordinated. Such coordination is usually undertaken through optimization models that use hydro plants to minimize total electricity production cost subject to an array of prescribed constraints that ensure delivery of sufficient volumes of water to further sectors. In this context, we present a sub-optimal approach based on SDDP method to schedule power plants in a hydro-thermal system that presents non-convex irrigation constraints. We show applicability of this approach in the Chilean Central Interconnected System (SIC), where we accurately model current prescribed rules that coordinate water uses between electricity and agriculture sectors. We demonstrate that the presented SDDP-based approach determines feasible and near-optimal solutions with costs reasonably close to those optimally determined through alternative MILP formulation (that can properly capture non-convexity). We also found, however, that there may be issues associated with the levels of security of supply of the near-optimal solution since its stored water volumes tend to be lower than those associated with the optimum MILP solution.

Wetland Soil Carbon in a Watershed Context for the Prairie Pothole Region.

Wetland restoration in the Prairie Pothole Region (PPR) often involves soil removal to enhance water storage volume and/or remove seedbanks of invasive species. Consequences of soil removal could include loss of soil organic carbon (SOC), which is important to ecosystem functions such as water-holding capacity and nutrient retention needed for plant re-establishment. We used watershed position and surface flow pathways to classify wetlands into headwater or network systems to address two questions relevant to carbon (C) cycling and wetland restoration practices: (i) Do SOC stocks and C mineralization rates vary with landscape position in the watershed (headwater vs. network systems) and land use (restored vs. native prairie grasslands)? (ii) How might soil removal affect plant emergence? We addressed these questions using wetlands at three large (?200 ha) study areas in the central North Dakota PPR. We found the cumulative amount of C mineralization over 90 d was 100% greater for network than headwater systems, but SOC stocks were similar, suggesting greater C inputs beneath wetlands connected by higher-order drainage lines are balanced by greater rates of C turnover. Land use significantly affected SOC, with greater stocks beneath native prairie than restored grasslands for both watershed positions. Removal of mineral soil negatively affected plant emergence. This watershed-based framework can be applied to guide restoration designs by (i) weighting wetlands based on surface flow connectivity and contributing area and (ii) mapping the effects of soil removal on plant and soil properties for network and headwater wetland systems in the PPR.

Operation Planning Reservoir with Linear Programming Optimization Model for Water Demand of the Community In Aceh Besar District

On the condition before building a dam, Aceh Besar district often a shortage of water for the needs of the community, so that people difficulty in doing their activities. There is a river in the Aceh Besar district named “Keuliling River”. The river is one of the watershed sub-basins of Krueng Aceh which has large enough potential of water to increase the supply of raw water in order to meet the water needs of the Banda Aceh City and Aceh Besar district.Therefore, a reservoir building was built that able to acomodate a large capacity of water. The resorvoir was named “Keuliling Reservoir”. “Reservoir Keuliling” has 38.20 km2 watershed areas, 259.94 hectares wide puddle on Normal Water Front (MAN), a total of 18,359,078 m3 bin normal water level at an elevation of 45.80 m and has an effective pitcher of 12.99,208 m3. The reservoir also serves as a provider of raw water for the development of inland fisheries, livestock, rice fields and others. The greatest needs are to be served by the reservoir is water requirement for paddy planting season Rendeng in October to December and the gadu growing season from April to June. To meet all these requirements then performed the planning operation of reservoir. Ie, by optimizing the volume of water storage at the end of the month through the optimization of the use of inflow data and outflow data. The optimization performed with optimization models Linear Programming. The results of the optimization is the volume of water in reservoirs that have large water needs, which in October is 13,380,986 m3, in November is 76,640,036 m3 and in December is 38,104,116 m3. Where in each month of the above conditions are still effective volume reservoirs at 12,992,080 m3. The results showed that from month to month never happened reservoir conditions at the level of the dead reservoirs, this illustrates that Keuliling reservoir can meet the water needs of the community.

The implications of water storage for human settlement in Mediterranean waterless islands: The example of Pantelleria

Consistent water supply is a common issue in the history of Mediterranean civilizations, where hydraulic solutions, such as cisterns, wells, reservoirs and aqueducts, were adopted for private and public supply. In this context, the island of Pantelleria, where surface freshwater is virtually non-existent, represents a unique case for understanding human–environment interaction in waterless environments. Here, in historical times, year-round water supply was only possible through the storage of rainwater in underground cisterns. An intensive field survey carried out across the island led to the discovery of hundreds of cisterns dated from the Punic and Roman periods to the present day. The study of the spatial distribution of the cisterns was compared with archaeological data on the island to gain new insights on historical settlement and demographic patterns. The present work focusses on a semi-quantitative assessment of water storage on the island of Pantelleria based on the evaluation of potential volumes of stored water for different periods. Data available for cisterns in Pantelleria have been analysed and compared with those from coeval Mediterranean regions. Calculations on the seasonal fluctuation between water demand and supply have been estimated to evaluate the efficiency of such system for sustaining human population and subsistence activities through time.

Hysteretic relationships in inundation dynamics for a large lake–floodplain system

Large lake floodplains have important roles in mitigating floods and providing vital habitats for wetland biota. This paper explores the hydrology of the extensive floodplains of Poyang Lake (China) to highlight complex, hysteretic relationships in the inundation dynamics, which are controlled by the heterogeneity of the land surface and time-varying exchanges between the Lake, its catchment and the Yangtze River. A physics-based hydrodynamic model of the system was used to evaluate the development and degree of hysteresis in the relationships between the flooded area, the water storage volume and the water level elevation. The modeling results indicate that the degree of hysteresis varies spatially with point of reference within the Lake. It is noted that a clockwise hysteresis is present for the majority of the Lake, but a counter-clockwise hysteresis is present at the upstream boundary, similar to a river–floodplain behavior. Both the floodplain and the permanently inundated region contribute to Poyang Lake’s volume–stage hysteretic effects. The time-varying inflow from rivers in the catchment is the major factor affecting hysteresis, rather than Yangtze River controls on Lake discharge. As expected, an increase in land surface roughness (representing denser vegetation cover) produced greater hysteresis, most notably in the storage curve and derived mainly from the floodplain region. Hysteresis is an important characteristic of the floodplain hydrology that needs to be incorporated in simpler models of the inundation dynamics to avoid errors of up to 50% in the floodplain water storage. The current study shows for the first time the hysteretic nature, and its major causal factors, of the hydrology of a large lake–floodplain system. An improved understanding of Poyang Lake floodplain behavior is offered to guide the future development of water management models.

Mapping wetland water depths over the central Congo Basin using PALSAR ScanSAR, Envisat altimetry, and MODIS VCF data

We have, for the first time, developed a simple linear regression model based on PALSAR ScanSAR backscattering coefficients (σ0), water levels from Envisat altimetry, and MODIS Vegetation Continuous Field (VCF) product to generate water depth maps over flooded forest in the central Congo Basin. The water depth maps we generated are relative to the lowest water level from Envisat altimetry, which is assumed to be a base level with essentially zero depth. The predicted and observed water depths along the Envisat pass showed excellent agreements with RMS differences of 12.8cm to 17.8cm. The water depth maps were also independently validated with ∂h/∂t obtained from PALSAR interferometry, and storage anomalies estimated by multiplying inundation extents from PALSAR ScanSAR with spatially averaged water level anomalies from Envisat altimetry. The water storage volumes calculated from our water depth maps were calculated to be 11.3±2.0km3, 10.3±2.3km3, and 9.3±1.8km3 for 12/05/2006, 12/08/2007, and 12/10/2008, respectively. It is expected that our method can be applied to other river basins that have flooded forest with satellite radar altimeter over-passes. The water depth maps can be directly used to calibrate and validate the spatial and temporal variation of inundation extent and water depth in the wetland derived from a 2-D hydrodynamic model. Furthermore, our water depth maps can be used as a “true” dataset to perform a pre-launch “virtual mission” study of the Surface Water Ocean Topography (SWOT) mission to be launched in 2020.

Surface Freshwater Storage Variations in the Orinoco Floodplains Using Multi-Satellite Observations

Variations in surface water extent and storage are poorly characterized from regional to global scales. In this study, a multi-satellite approach is proposed to estimate the water stored in the floodplains of the Orinoco Basin at a monthly time-scale using remotely-sensed observations of surface water from the Global Inundation Extent Multi-Satellite (GIEMS) and stages from Envisat radar altimetry. Surface water storage variations over 2003–2007 exhibit large interannual variability and a strong seasonal signal, peaking during summer, and associated with the flood pulse. The volume of surface water storage in the Orinoco Basin was highly correlated with the river discharge at Ciudad Bolivar (R = 0.95), the closest station to the mouth where discharge was estimated, although discharge lagged one month behind storage. The correlation remained high (R = 0.73) after removing seasonal effects. Mean annual variations in surface water volume represented ~170 km3, contributing to ~45% of the Gravity Recovery and Climate Experiment (GRACE)-derived total water storage variations and representing ~13% of the total volume of water that flowed out of the Orinoco Basin to the Atlantic Ocean.

Surface Freshwater Storage Variations in the Orinoco Floodplains Using Multi-Satellite Observations

Variations in surface water extent and storage are poorly characterized from regional to global scales. In this study, a multi-satellite approach is proposed to estimate the water stored in the floodplains of the Orinoco Basin at a monthly time-scale using remotely-sensed observations of surface water from the Global Inundation Extent Multi-Satellite (GIEMS) and stages from Envisat radar altimetry. Surface water storage variations over 2003–2007 exhibit large interannual variability and a strong seasonal signal, peaking during summer, and associated with the flood pulse. The volume of surface water storage in the Orinoco Basin was highly correlated with the river discharge at Ciudad Bolivar (R = 0.95), the closest station to the mouth where discharge was estimated, although discharge lagged one month behind storage. The correlation remained high (R = 0.73) after removing seasonal effects. Mean annual variations in surface water volume represented ~170 km3, contributing to ~45% of the Gravity Recovery and Climate Experiment (GRACE)-derived total water storage variations and representing ~13% of the total volume of water that flowed out of the Orinoco Basin to the Atlantic Ocean.

Effect of exposure on the water balance of two identical lysimeters

Summary This study looks at the water balance of two identical weighable lysimeters located right next to each other. They contain the same soil and are managed in the same way. Both were planted with maize. The area around them was planted with maize, too, to ensure that the lysimeters were located inside a crop. The only difference between them was that one side of lysimeter 2 was exposed due to a footpath. At first both yielded similar results. However, as the maize became taller lysimeter 2 began to show consistently more precipitation and drainage. After harvest the differences disappeared again. Since precipitation often falls at an angle, a crop with an exposed side receives more than a crop without one, if the precipitation falls towards the exposed side. The additional precipitation a crop with an exposed side may capture increases with the height of the crop. After harvest this exposure effect therefore disappears completely. Compared to lysimeter 1, lysimeter 2 accumulated >100 mm of additional precipitation during the growth of the maize. After the maize was removed, both crops recorded the same amount of precipitation again. Lysimeter 2 showed more drainage, too, because the additional precipitation led to higher water contents, which in turn caused the water holding capacity of the soil to be exceeded on more days than in the case of lysimeter 1. The difference in actual evapotranspiration was small, because lysimeter 2 was exposed towards west-northwest and therefore received only little more radiation, and because the distribution of the rainfall pattern was such that the additional precipitation led to a similar amount of additional drainage rather than to an increase in the volume of stored water, which could have been consumed by evapotranspiration later. The data clearly illustrate that exposure can significantly alter the water balance of a lysimeter, which makes it inadvisable to extrapolate data obtained under such circumstances to the field. This should be well known to people working with lysimeters. However, apparently it is not, because there are many lysimeters in operation which have one or more exposed sides. The objective of this paper is to bring this problem back to mind.