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Search Results: 1 - 10 of 587 matches for " Evapotranspiration "
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Reed Beds for Sludge Dewatering and Stabilization  [PDF]
Manoj Kumar Pandey, Petter Deinboll Jenssen
Journal of Environmental Protection (JEP) , 2015, DOI: 10.4236/jep.2015.64034
Abstract: In urban and peri-urban areas of developing countries decentralized wastewater treatment using septic tanks as pretreatment is common. One challenge of decentralized wastewater treatment systems (DEWATS) is handling and utilization of the generated sludge. Sludge drying reed beds (SDRBs) are a robust method for dewatering and stabilization of sludge. Constructed wetlands (CWs) and SDRBs can be integrated to treat both wastewater and sludge. SDRBs require more area than most other sludge treatment options, but have low operational cost and energy requirements. The land area required for SDRB’s can be optimized by the selection of an appropriate loading rate, sludge application frequency and resting phase. This paper gives a review regarding the use of SDRB’s as well as presenting a pilot scale experiment comparing planted and unplanted sludge drying beds in Kathmandu. The planted beds showed a higher dewatering capability and higher reduction of volatile solids (VS). A short-term pilot-scale experiment can give valuable input to the design and operation of full-scale systems and for sub-tropical climate as that of Kathmandu Nepal, an initial sludge loading rate (SLR) of 100 kg total solids (TS)/m2/year is suggested with a gradual increase to up to 250 kg TS/m2/year.
Groundwater Annual Dynamics in the Basins of Woro and Chago (Eastern Niger) as Affected by Seasonal Variability and Anthropic Activities  [PDF]
Adamou Mahaman Moustapha, Nazoumou Yahaya, Aw Sadat, Awaiss Yahaya, Ambouta Karimou
Journal of Water Resource and Protection (JWARP) , 2013, DOI: 10.4236/jwarp.2013.59094

The Sahelian region is known to have extremes climatic constraints since the end of the seventies. The studied zone is characterized by an extreme spatial and temporal variability of the environmental factors, complicating the understanding of the mechanisms governing the functioning of the hydrological system in the basin. The evapotranspiration was very high (1975 mm/an), whereas the local annual rainfall was around 300 mm/year. The piezometric data showed a rise of the groundwater level during the rainy season and a decrease in the dry season. The water balance obtained using the Penman-Monteith method showed the predominance of the evapotranspiration (75% to 80% of the rainfall) on the drainage (20% to 25% of the precipitations).

Estimation of Evapotranspiration from Faber Fir Forest Ecosystem in the Eastern Tibetan Plateau of China Using SHAW Model  [PDF]
Zhifang Yin, Hua Ouyang, Xingliang Xu, Caiping Zhou, Feng Zhang, Bin Shao
Journal of Water Resource and Protection (JWARP) , 2010, DOI: 10.4236/jwarp.2010.22017
Abstract: Understanding the hydrological processes of forest ecosystems in Tibetan Plateau is crucial for protecting water resources and the environment, especially considering that evapotranspiration is the most dominant hydrologic process in most forest systems. SHAW, as a physically based, hydrological model, provides a useful tool for understanding and analyzing evapotranspiration processes. Using the measured data of a faber fir forest ecosystem in eastern Tibetan Plateau, this paper assessed the model performance in simulating evapotranspiration and variability and transferability of the model parameters. Comparison of the simulated results by SHAW to the measured data showed that SHAW performed satisfactorily. Based on analyzing the simulated results by the calibrated and validated SHAW, some ET characteristics of faber fir forest ecosys-tem in the eastern Tibetan Plateau were found: 1) Daily plant transpiration is low, and daily ET mainly comes from surface evaporation including canopy, litter and soil evaporation. Peak ET rate was approxi-mately 4mm/day, occurring around late July. 2) Solar radiation is the most important factor accounting for daily ET variation, while air temperature is the secondary, wind speed and air relative humidity are minor and soil water storage is the least important among all the related factors. 3) The ratio of annual ET to pre-cipitation for the faber fir forest ecosystem in eastern Tibetan Plateau is low (18%) compared with the other forest ecosystems owing to high-elevation, high atmospheric humidity and low annual temperature.
Thermal Classification of Pakistan  [PDF]
Maida Zahid, Ghulam Rasul
Atmospheric and Climate Sciences (ACS) , 2011, DOI: 10.4236/acs.2011.14023
Abstract: This research work is designed to carry out the annual and seasonal thermal classification of Pakistan to provide better understanding to all the stake holders like farmers and scientists etc for obtaining maximum crop yield. The data of Climatic Normal’s (1971-2000) has been used to calculate Thornthwaites’s Thermal efficiency index for thermal classification of Pakistan. The results of annual thermal classification reveals that Pakistan’s northern half experiences Tundra to Microthermal climate type and southern half experiences all types of Mesothermal to Megathermal climate type. Seasonal analysis showed large variations like in winters the whole country ranges from Microthermal to Frost Type of climate except the extremely southern parts of the country which have Mild Mesothermal climate. In spring the northern half of the country lies between Tundra to Microthermal climate and southern half from Mesothermal to Megathermal climate. During summer and monsoon majority of the regions in the country experience Megathermal except Northern areas which show Moderate Mesothermal to Mesothermal climate. The autumn season mostly have Mild Mesothermal to Tundra climate excluding southern half which showed Moderate Mesothermal to Mesothermal climate.
Water requirements and single and dual crop coefficients of sugarcane grown in a tropical region, Brazil  [PDF]
Vicente de P. R. da Silva, Cícera J. R. Borges, Carlos H. A. Farias, Vijay P. Singh, Walker G. Albuquerque, Bernardo Barbosa da Silva
Agricultural Sciences (AS) , 2012, DOI: 10.4236/as.2012.32032
Abstract: A field experiment was conducted throughout 2009/2010 in a sugarcane field of a commercial distillery located on the coastal area of Paraiba state, Brazil. The objectives were to determine sugarcane water requirements and to test the single and dual crop coefficients by comparing the calculated values of ET with measured ones. Crop evapotranspiration was determined by field water balance, reference evapotranspiration (ETo) by the Penman-Monteith approach, while single and dual crop coefficients were computed through the standard FAO-56 methodology. The experimental area was cultivated with irrigation applied weekly by a centre pivot system in addition to rainfall and the irrigation scheduling was based on 100% ETo. Three statistical tests, mean bias difference (MBD), normalized root mean square difference (NRMSD) and regression analysis, were used to evaluate the performance of single and dual crop coefficients. Results showed that there was a notable symmetry between ET measured and ET calculated by Kc dual. The ET values, calculated from Kc single, underestimated those obtained from soil water balance measurements by 36%.
Application of MODIS-Based Monthly Evapotranspiration Rates in Runoff Modeling: A Case Study in Nebraska,USA  [PDF]
Jozsef Szilagyi
Open Journal of Modern Hydrology (OJMH) , 2013, DOI: 10.4236/ojmh.2013.34021
Abstract: Daily and monthly flow-rates of the Little Nemaha River in Nebraska were simulated by the lumped-parameter Jakeman-Hornberger as well as a distributed-parameter water-balance accounting procedure for the 2003-2008 and 2000-2009 periods, respectively, with and without the help of the MODIS-based monthly estimates of evapotranspiration (ET) rates. While the daily lumped-parameter model simulation accuracy remained practically unchanged with the inclusion of the monthly MODIS-based ET rates interpolated into daily values (R2 of 0.66 vs 0.68, simulated to measured runoff ratio remaining the same 96%), the monthly water-balance accounting model outcomes did improve to some extent (from an R2 of 0.67 to 0.7 with simulated to measured runoff ratio of 72% vs 115%). In both cases the models had to be slightly modified for accommodation of the ET rates as predefined input values, not present in the original model setups. These results indicate the potential practical usefulness of satellite-derived ET estimates (CREMAP values in the present case) in monthly water-balance modeling. CREMAP is a calibration-free ET estimation method based on MODIS-derived daytime surface temperature values in combination of basic climatic variables, such as air temperature, humidity and solar radiation within a Complementary Relationship framework of evaporation.
Water Stress Estimation from NDVI-Ts Plot and the Wet Environment Evapotranspiration  [PDF]
Daniela Girolimetto, Virginia Venturini
Advances in Remote Sensing (ARS) , 2013, DOI: 10.4236/ars.2013.24031

In this work we present a new simple index to estimate water stress (WS) for different types of surfaces, from remotely sensed data. We derive a WS index, named WSIEw, modifying the Water Deficit Index (WDI) proposed by Moran et al. by using the wet environment evapotranspiration (Ew) instead of the potential evapotranspiration (Epot) concept. Jiang and Islam model was used to simulate actual evapotranspiration (ET) and Priestley and Taylor equation to estimate Ew. The WSIEw results were compared to ground observations of ET, precipitation (PP), soil temperature (Tsoil) and soil moisture (SM) in the Southern Great Plains-EEUU. Preliminary results suggest the method is sensitive to the water status of different surfaces. However, the WSIEw would range from 0 to 0.7, having a value of 0.4 for a dry surface with 5% of SM. The methodology is operationally

Energy Balance in a Patch of the Atlantic Forest in São Paulo City, Brazil  [PDF]
Frederico Luiz Funari, Augusto José Pereira Filho
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.69076

The aim of this work was to characterize and to bring into relationship of the net radiation with the latent heat flux equivalent to water (mm) in a patch of Atlantic Forest within the metropolitan area of Sao Paulo (RMSP). The estimation of the latent heat flux (LE) was made by the energy balance equation with the Bowen ratio. Measurements of net radiation and psychometrics gradients were made. Soil heat flux (G) was measured by temperature sensors in two depths. Measurements were made at Park of Science and Technology of Sao Paulo University (CIENTEC), Sao Paulo, Brazil, between 2011 and 2013. Results indicated that evapotranspiration varies seasonally and the amount of water evaporated exceeds 3.0 mm·day-1 in spring/summer and in autumn/winter the amount is approximately 1.0 mm·day-1. The evapotranspiration is increased under RMSP urban climate conditions with higher air temperature and lower moisture especially in summer season.

Measuring Autogenic Recharge over a Karst Aquifer Utilizing Eddy Covariance Evapotranspiration  [PDF]
Nico M. Hauwert, John M. Sharp
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.69081

Autogenic, or direct aquifer recharge can best be measured as the remainder of a water balance utilizing precise measurement of precipitation, evapotranspiration (ET) and runoff. ET is the largest component of a precipitation water balance and can be measured within 5% using an eddy covariance system with Bowen-ratio energy balance corrections. Water balance components of precipitation, evapotranspiration, internal runoff, soil moisture were measured using a eddy covariance system, tipping bucket and visual rain gauges, flumes, and soil-moisture sensors. The research site was located within a 0.19-km2 (46-acre) internal drainage sinkhole basin where runoff never flows beyond the basin, but potentially reaches a cave serving as a drain to the sinkhole. Other than the cave drain, the basin slopes are indistinguishable from other slopes across the Barton Springs Segment of the Edwards Aquifer. Over a 505-day water balance interval where change in soil moisture was negligible and precipitation was 42% above average, ET was 68% of precipitation, discrete internal runoff was 6%, and remaining component of diffuse autogenic recharge was measured as the residual of total rainfall as 26% of rainfall. Over a longer period of average rainfall, internal runoff diminished to 3%, but was as high as 42% of precipitation during single storms when the soils were near saturation. These results closely match results from a five-year water balance over the Trinity Aquifer of Central Texas where ET was measured to be 65% of precipitation using a Bowen-ratio climate tower, runoff was measured to be 5% of precipitation, and recharge was calculated as the residual at 30% of rainfall. ET flux tower data from other sites across Central Texas indicate that under average precipitation conditions, autogenic recharge is about 28% and intervening recharge area runoff is about 3% of precipitation. During years of higher than average precipitation, authogenic recharge and intervening recharge area runoff combined increase within the range of 30% to 45% of precipitation.

Influence of Potential Evapotranspiration on the Water Balance of Sugarcane Fields in Maui, Hawaii  [PDF]
Javier Osorio, Jaehak Jeong, Katrin Bieger, Jeff Arnold
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.69080

The year-long warm temperatures and other climatic characteristics of the Pacific Ocean Islands have made Hawaii an optimum place for growing sugarcane; however, irrigation is essential to satisfy the large water demand of sugarcane. Under the Hawaiian tropical weather, actual evapotranspiration (AET) is the primary mechanism by which water is removed from natural and agricultural systems. The Hawaiian Commercial and Sugar Company (HC&S), the largest sugarcane grower of the Hawaiian Islands, has developed a locally optimized AET equation for the purpose of water management on its 184.3 km2 sugarcane plantation on the Island of Maui. In this paper, in order to assess the influence of AET on the hydrological water balance of the HC&S’ sugarcane cropping system, the performance of the HC&S method was compared with three physically-based methods: Penman-Monteith, Priestley-Taylor, and Hargreaves, as well as, to a set of historical pan evaporation data. A Soil and Water Assessment Tool (SWAT) project was setup to estimate the water balance in two sugarcane fields: a windy lowland field and a rocky highland field on a hill slope. Under Hawaiian weather conditions, wind speed was found to be the most influential climatic parameter over potential evapotranspiration (PET); therefore, the results with both Hargreaves and Priestley-Taylor underpredicted PET by approximately 30%, presumably because these methods do not take wind speed into account. The HC&S method was demonstrated to be the most accurate PET method compared to the other commonly used PET equations, with less than 10% error. Of the annual total water supply of 3400 mm, AET accounted for 75% - 80% of the total water consumption. These findings can be used to improve the irrigation efficiency as well as other management scenarios to optimize water use on the Island of Maui.

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