Free Water Surface Evaporation Research Articles

Optimal Calibration of Evaporation Models against Penman–Monteith Equation

We present an approach for the calibration of simplified evaporation model parameters based on the optimization of parameters against the most complex model for evaporation estimation, i.e., the Penman–Monteith equation. This model computes the evaporation from several input quantities, such as air temperature, wind speed, heat storage, net radiation etc. However, sometimes all these values are not available, therefore we must use simplified models. Our interest in free water surface evaporation is given by the need for ongoing hydric reclamation of the former Ležáky–Most quarry, i.e., the ongoing restoration of the land that has been mined to a natural and economically usable state. For emerging pit lakes, the prediction of evaporation and the level of water plays a crucial role. We examine the methodology on several popular models and standard statistical measures. The presented approach can be applied in a general model calibration process subject to any theoretical or measured evaporation.

The Calibration of Evaporation Models against the Penman–Monteith Equation on Lake Most

Evaporation is one of the main components of the water cycle in nature. Our interest in free water surface evaporation is due to the needs of ongoing hydric recultivation of the former Ležáky–Most quarry, i.e., Lake Most, and also other planned hydric recultivations in the region. One of the key components of hydric reclamation planning is the securitization of long-term sustainability, which is based on the capability to keep the final water level at a stable level. In our work, we are interested in the evaporation estimation in the area of Lake Most (Czech Republic, Europe). This lake has been artificially created only a few years ago, and nowadays we are looking for a simple evaporation model, based on which we will be able to decide which measurement devices have to be installed at the location to provide more localized data to the model. In this paper, we calibrate state-of-the-art simplified evaporation models against the Penman–Monteith equation based on the Nash–Sutcliffe efficiency maximization. We discuss the suitability of this approach using real-world climate data from the weather station located one km from the area of interest.

Development of mass-transfer evaporation model for Lake Nasser, Egypt

Abstract Evaporation from free water surface is considered a very important constituent in both the energy and hydrologic cycles. Precise measurement of evaporation from the free water surface is almost impossible. This is why we need a calculation model for free water evaporation. In this study, a simple mass-transfer evaporation model was developed to be applicable over Lake Nasser in the hyper-arid region located in the south of Egypt. Measured meteorological data (2011–2014) at two stations, Aswan and Abu-Simbel, were used to calculate free water surface evaporation using Priestly–Taylor equation. Priestly–Taylor equation was used because it is the most appropriate equation for Lake Nasser evaporation according to the literature. Results from this model were used to develop a simple mass-transfer evaporation model. The statistical analysis for both calibration and validation periods were very good. The slope of the regression line is about 0.9, with a coefficient of determination of 0.98. The t value is 0.6, at p value of 0.544, which is much greater than 0.05. The developed model could be used with confidence at Aswan meteorological station or on the average of the two meteorological stations, while it should be used carefully on Abu-Simbel meteorological station.

Assessment of various vaporisation methods related for reservoir in the Northern Region of Gujarat, India

Evaporation from water surfaces as an essential component for efficient management of reservoirs, particularly in water-scarce areas in India. Evaluating performance of seven empirical methods based on ten years meteorological data, the most effective and reliable evaporation estimates model for Dharoi reservoir (India) has been derived while comparing monthly, yearly and seasonal basis with observed pan values. The various goodness of fit measures, such as; coefficient of determination (R2), index of agreement (D), root mean square error (RMSE), and relative bias (RB) have been chosen for the performance evaluation. After application of correction factor in Penman, the value of R2, RSME, RB and D are 0.81, 0.61, 0.10 and 0.94 respectively shows good agreement with Pan value. Other models are showing good fitness with Pan but, the parameters considered in Penman is more and important for evaluation of evaporation. Hence Penman method can successfully be extensive for free water surface evaporation estimates in Dharoi reservoir, part of semi-arid region of Gujarat, India.

Evaluating the best evaporation estimate model for free water surface evaporation in hyper-arid regions: a case study in the Ejina basin, northwest China

Free water surface evaporation is an important process in the hydrologic and energy cycle. Accurate calculation of free water evaporation helps in evaluating the reliability of data on the distribution and quantity of water resources. However, the applicability of evaporation models to the calculation of free water surface evaporation in hyper-arid regions is still uncertain. Moreover, the accuracy of previously used evaporation models should be evaluated for hyper-arid regions. In this study, the Ejina basin in the hyper-arid region of northwest China was selected to address this issue. Measured meteorological data (1993–2008) were used to calculate free water surface evaporation using the Dalton model, Penman formula, and energy balance equations. Results from two different Dalton models were higher and lower than the results from E601 pan evaporation, respectively. Results from the Penman formula were lower than results from E601 pan, whereas results from the energy balance equations are higher than the results from E601 pan. The results indicate that previous evaporation models are not suited for calculating free water surface evaporation in hyper-arid regions if not modified. Using meteorological data and radiation data (1993–2000), the Dalton model, energy balance equations, and Penman formula were modified to calculate free water surface evaporation for 2001–2008. The average annual evaporation from the three modified models was slightly lower than the evaporation from E601 pan during 2001–2008. However, the errors in the values were only 11–14 mm, which were much lower than in previous models. The modified Dalton model and Penman formula yielded a higher accuracy of the calculation, whereas the modified energy balance equations had the lowest accuracy.

Inter-annual and spatial variability of Hamon potential evapotranspiration model coefficients

Summary Monthly calibrated values of the Hamon PET coefficient (C) are determined for 109,951 hydrologic response units (HRUs) across the conterminous United States (U.S.). The calibrated coefficient values are determined by matching calculated mean monthly Hamon PET to mean monthly free-water surface evaporation. For most locations and months the calibrated coefficients are larger than the standard value reported by Hamon. The largest changes in the coefficients were for the late winter/early spring and fall months, whereas the smallest changes were for the summer months. Comparisons of PET computed using the standard value of C and computed using calibrated values of C indicate that for most of the conterminous U.S. PET is underestimated using the standard Hamon PET coefficient, except for the southeastern U.S.

Comparison of Different Ann Approaches in Daily Pan Evaporation Prediction

Nowadays, one of the most important effects on water resources under climate change is increasing of free water surface evaporation which depends on the increasing of temperature. In basins, where there are no observed data, free water surface evaporation is taken into account depending on historical temperature and similar data and their long-term statistics. Predicting of real value of evaporation contains some uncertainties. The modeling of evaporation with a small number of predictors has crucial importance on the regions and basins where measurements are not sufficient and/or not exist. In this presented study, daily evaporation prediction models were prepared by using empirical Penman equation, Levenberg-Marquardt algorithm based on "Feed Forward Back Propagation Artificial Neural Networks (LMANN)", radial basis neural networks (RBNN), generalized regression neural networks (GRNN). When the models were compared, it was noticed that the results of neural network models are statistically more meaningful than the Penman equation.

Global off-line evaluation of the ISBA-TRIP flood model

This study presents an off-line global evaluation of the ISBA-TRIP hydrological model including a two-way flood scheme. The flood dynamics is indeed described through the daily coupling between the ISBA land surface model and the TRIP river routing model including a prognostic flood reservoir. This reservoir fills when the river height exceeds the critical river bankfull height and vice versa. The flood interacts with the soil hydrology through infiltration and with the overlying atmosphere through precipitation interception and free water surface evaporation. The model is evaluated over a relatively long period (1986-2006) at 1 degrees resolution using the Princeton University 3-hourly atmospheric forcing. Four simulations are performed in order to assess the model sensitivity to the river bankfull height. The evaluation is made against satellite-derived global inundation estimates as well as in situ river discharge observations at 122 gauging stations. First, the results show a reasonable simulation of the global distribution of simulated floodplains when compared to satellite-derived estimates. At basin scale, the comparison reveals some discrepancies, both in terms of climatology and interannual variability, but the results remain acceptable for a simple large-scale model. In addition, the simulated river discharges are improved in term of efficiency scores for more than 50% of the 122 stations and deteriorated for 4% only. Two mechanisms mainly explain this positive impact: an increase in evapotranspiration that limits the annual discharge overestimation found when flooding is not taking into account and a smoothed river peak flow when the floodplain storage is significant. Finally, the sensitivity experiments suggest that the river bankfull depth is potentially tunable according to the river discharge scores to control the accuracy of the simulated flooded areas and its related increase in land surface evaporation. Such a tuning could be relevant at least for climate studies in which the spatio-temporal variations in precipitation are generally poorly represented.

Root Water Uptake and Root Nitrogen Mass of Winter Wheat and Their Simulations

In this study, winter wheat (Triticum aestivum L.) was grown in nutrient solution (Exp. 1) and soil columns (Exp. 2) under controlled environmental conditions to investigate the relationship between root water uptake (RWU) and root N mass (RNM). In Exp. 1, 15 treatments were designed to examine the influence of NO3 concentrations (0.007–0.42 kg m−3) and illumination conditions (free water surface evaporation rates of 0.25–0.47 cm d−1) on root N content (RNC) and RWU. Measurements included transpiration, dry weight, N content, and root length. In Exp. 2, RNC and RWU of wheat were measured at two NO3 levels (0.011 and 0.105 kg m−3) and low and high (80% field water capacity) soil water contents. The distributions of soil water content, NO3 concentration, RNM density, root length density, and soil temperature were observed. Results showed that the potential transpiration was proportional to RNM of wheat (R2 = 0.99), and the maximum RWU rate, Smax, which changed from 0 to 0.023 m3 m−3 d−1, was also linearly related to the RNM density (R2 = 0.78). The ratio between potential transpiration and RNM, namely the potential RWU coefficient per unit RNM, was independent of environmental NO3 level and wheat maturity, but changed linearly with the free water surface evaporation rate (R2 = 0.88). The relationship between RWU and RNM was applied to simulate the distributions of soil water content, soil NO3 concentration, and RNM density in Exp. 2. The simulated results compared well with the measured data, and the maximum RMSEs were 0.0085 m3 m−3, 0.0283 kg m−3, and 0.0009 kg m−3, respectively.

Atmosphere and hydrological controls of the evapotranspiration over a floodplain forest in the Bananal Island region, Amazonia

This article discusses seasonal and interannual variations of the evapotranspiration (ET) rates in Bananal Island floodplain, Brazil. Measurements included ET and sensible heat flux using the eddy covariance method, atmospheric forcings (net radiation, Rn, vapor pressure deficit, VPD, wind speed and air temperature), soil moisture profiles, groundwater level and flood height, taken from November 2003 to December 2006. For the hydrological years (October‐September) of 2003/2004, 2004/2005 and 2005/2006, the accumulated precipitation was 1692, 1471, 1914 mm and the accumulated ET was 1361, 1318 and 1317 mm, respectively. Seasonal analyses indicated that ET decreased in the dry season (average 3.7 mm day−1), despite the simultaneous increase in Rn, air temperature and VPD. The increase of ET in the wet season and particularly in the flood period (average 4.1 mm day−1) showed that the free water surface evaporation strongly influenced the energy exchange. Soil moisture, which was substantially depleted during the dry season, and adaptative vegetation mechanisms such as leaf senescence contributed to limit the dry season ET. Strong drainage within permeable sandy soils helped to explain the soil moisture depletion. These results suggest that the Bananal flooding area shows a different pattern in relation to the upland Amazon forests, being more similar to the savanna strictu senso areas in central Brazil. For example, seasonal ET variation was not in phase with Rn; the wet season ET was higher than the dry season ET; and the system stored only a tiny memory of the flooding period, being sensitive to extended drought periods.

A new river flooding scheme for global climate applications: Off‐line evaluation over South America

Given their strong interaction with both climate and the carbon cycle, wetlands and surface waters need to be parameterized in global general circulation models. For this purpose, a new simple flooding river scheme is proposed and evaluated over South America. The flood dynamics is described through the coupling between the ISBA land surface model and the TRIP river routing model including a prognostic flood reservoir. This reservoir fills when the river height exceeds a critical value and vice versa. The reservoir interacts with the soil hydrology through infiltration and with the overlying atmosphere through precipitation interception and free water surface evaporation. The model is tested in off‐line mode using the 10‐year ISLSCP‐2 atmospheric forcing. The evaluation is made against satellite‐derived inundation estimates as well as in situ river discharge observations. Besides a basin‐scale increase in annual surface evaporation, the results show improved monthly discharges over the Amazon and Parana rivers, as well as a reasonable agreement between the simulated flooded areas and satellite‐derived inundation estimates.

Evaluating best evaporation estimate model for water surface evaporation in semi‐arid region, India

AbstractEvaluating performances of four commonly used evaporation estimate methods, namely; Bowen ratio energy balance (BREB), mass transfer (MT), Priestley–Taylor (PT) and pan evaporation (PE), based on 4 years experimental data, the most effective and the reliable evaporation estimates model for the semi‐arid region of India has been derived. The various goodness‐of‐fit measures, such as; coefficient of determination (R2), index of agreement (D), root mean square error (RMSE), and relative bias (RB) have been chosen for the performance evaluation. Of these models, the PT model has been found most promising when the Bowen ratio, β is known a priori, and based on its limited data requirement. The responses of the BREB, the PT, and the PE models were found comparable to each other, while the response of the MT model differed to match with the responses of the other three models. The coefficients, β of the BREB, µ of the MT, α of the PT and KP of the PE model were estimated as 0·07, 2·35, 1·31 and 0·65, respectively. The PT model can successfully be extended for free water surface evaporation estimates in semi‐arid India.A linear regression model depicting relationship between daily air and water temperature has been developed using the observed water temperatures and the corresponding air temperatures. The model helped to generate unrecorded water temperatures for the corresponding ambient air temperatures. Copyright © 2007 John Wiley & Sons, Ltd.

Investigating the conversion coefficients for free water surface evaporation of different evaporation pans

AbstractThe conversion coefficients of free water surface evaporation were investigated. Comparisons were made between numerous evaporation tanks (pans) and a 20 m2 evaporation tank. Based on 6 years of evaporation data collected at Nansihu Lake Evaporation Station in Shandong Province, China, the following results have been obtained. First, conversion coefficients varied according to the evaporator type. The average yearly conversion coefficient was only 0·60 for ϕ20 evaporator (an evaporation pan with a diameter of 20 cm), whereas it was about 1·07 for the E601's pan, whose rim was about 7·5 cm above ground. Second, the conversion coefficient changes within a year had the same pattern among the evaporators evaluated. The monthly conversion coefficients had the minimum values in March or April, then increased with time, and reached their maximum values in August or September. After September, the conversion coefficients varied in different directions with time. Third, the conversion coefficients changed from year to year, but their variations between maximum and minimum values were between 0·06 and 0·16. Fourth, the installation modes, structures, and composition of the evaporators affected the evaporation amount. Fifth, the conversion coefficients at Nansihu and Yucheng stations for the same evaporator did not show a distinct difference. The E601 evaporator has almost the same conversion coefficients at six of seven stations spanning almost 20° in latitude from northern to southern China. Sixth, the yearly evaporation from a 100 m2 evaporation tank was almost the same as that from the 20 m2 evaporation tanks; however, the differences still existed in any given month. Copyright © 2004 John Wiley & Sons, Ltd.

Effects of Different Irrigation Methods on Yield, Evapotranspiration and Root Development of Young Orange Trees

In this study, trickle (drip, D) and mini-sprinkler (MS) irrigation methods were compared in an orange (cv. Washington Navel) orchard in 1981-1987. Soil moisture content in the sprinkler irrigated plots was brought to field capacity by irrigations applied at 40-50 percent of available soil moisture capacity of 90 cm root depth. In trickle systems, the amount of irrigation was calculated using free water surface evaporation (CAP), and four different pan coefficients that varied from 0.60 to 1.20 by 0.20 increments. Irrigations were applied at two days intervals. The yields for both irrigation methods increased continuously in the trial years. Fruit yields were 1344 kg/da for sprinkler, and 534 to 771 kg/da for trickle methods in the last trial year. There was no statistical significant differences between yields in the trickle applications. Although the highest yields were obtained for trickle irrigation (p Keywords:

Estimating pan evaporation using limited meteorological observations

Pan evaporation measurements have been used worldwide as a means of estimating evapotranspiration and free water surface evaporation. The availability of pan evaporation measurements is critical to many applications including irrigation scheduling, hydrologic modeling, and irrigation system design. The ability to predict daily pan evaporation based on limited meteorological observations is highly desirable. In many situations it is advantageous to calculate, rather than measure, pan evaporation. This is often the case in developing nations or remote locations where costs are prohibitive. Many relationships that predict pan evaporation or potential evapotranspiration as a function of limited meteorological observations have been developed. The relationships are often empirical, thus they suffer from lack of transferability. The relationship between potential evapotranspiration and pan evaporation facilitates local calibration of established equations using measured pan evaporation data. This calibration may then be extrapolated to locations that have similar climatic characteristics. A calibration procedure is presented and demonstrated by calibrating three equations using data from several sites located in the southeastern United States.

Substitution of small cans for weather bureau pans in measuring evaporation

Information about free-water surface evaporation on high mountain slopes is scarce because it is difficult to obtain a handy supply of water and to service research installations regularly in such remote locations. A recent study on areas at about 8200 feet elevation in the head of Parrish Canyon (Fig. 1) near Farmington, Utah, showed that small cans could be used to substitute for and to reduce the amount of ‘standard’ equipment needed. The small cans were much easier to service because only small amounts of replacement water were required. Plan of study. Evaporation was measured during the summers of 1957 and 1958 in Class A, 4-foot-diameter by 10-inch-deep, land surface pans and in 6.5-inch-diameter by 8.75-inch-deep cans [Weather Bureau, 1955]. The cans were shaded with horizontal sunshields of unpainted masonite because preliminary measurements indicated that water temperatures and evaporation were higher in the cans than in the pans.

Fertility investigations on the black earth wheatlands of the Darling Downs, Queensland. II. Moisture and evapotranspiration in relation to the wheat crop

The effects on wheat yields of available soil moisture at planting, rainfall during the growing period, and evapo-transpiration were examined for the years 1951-1954. The relation between free water surface evaporation, available soil moisture, and evapo-transpiration was examined for the years 1951 and 1952. Wheat yields were found to be correlated with available soil moisture at planting for the four years combined, the two drier years combined (1951 and l953), and the two wetter years combined (1952 and 1954). The relationship for the four years combined was sufficiently strong to suggest that available moisture at planting could be successfully used for yield prediction. Yield was correlated with evapo-transpiration only for the dry year 1953. The ratio of yield to evapo-transpiration was found to be lower for the years of high rainfall during the growing period, the mean values for the wet and dry years being 2.1 and 3.5 bus./in. respectively. Growing-perlod rainfall was correlated with yield only for the month of August for the two dry years of 1951 and 1953 combined. Evapotranspiration (Etr) was found to be correlated with free water surface evaporation (Ew) and Ew0.75 in the monthly data, the value for C in the relationship Etr = CEw0.75 being calculated as 0.53. Available soil moisture was correlated with evapo-transpiration using data from the beginning and end of the season in 1953, but was not correlated using monthly data. The method of calculating monthly available soil moisture is shown to be important in this correlation. A method of calculating available soil moisture over a monthly period, based on a mean daily figure for the month, is described.