Evaporation Ratio Research Articles

Performance prediction of a shower cooling tower using wavelet neural network

This paper develops an application of a wavelet neural network (WNN) based model to predict the performance of a shower cooling tower (SCT). In order to gather data to train and test the proposed WNN model, an experimental shower cooling tower was operated at some steady state conditions. Some of the experimental data are utilized for training. The model was used to predict various performance parameters of the system, namely the temperature difference of the outlet and inlet water stream and the dry bulb temperature, relative humidity of the outlet air stream, the water evaporative ratio and the cooling efficiency of the system. The performances of the WNN predictions were tested using experimental data not employed in the training process. The predictions yielded good agreement with the experimental values with correlation coefficients in the range of 0.9906–0.9986, mean relative errors in the range of 1.39–2.28% and very low root mean square errors. The results show that the WNN technique can be used effectively for predicting the performance characteristics of SCT under various operating conditions, then providing the theoretical basis on the research of heat and mass transfer inside SCT under any conditions, which is important for design and running control of the SCT system.

In-place HEPA filter testing by the sodium flame method

High-efficiency particulate air filter application involves three steps: filter media testing, filter testing, and in-place filter testing. In China, filter media testing and filter testing use the sodium flame method, which involves spraying an aqueous NaCl solution to produce NaCl aerosol. However, in-place filter testing cannot employ this approach because of the low dust production rate. The present study describes a sodium flame method in which a significant amount of NaCl aerosol is generated by burning a special salt bar. In the aerosol-producing experiment, some structural and operational parameters are determined by analyzing the NaCl aerosol production rate and evaporation ratio. These parameters include the spray angle of the burner, salt bar composition and diameter, inflammable gas type and flow rate, as well as the speed of gear device. In the aerosol measurement stage, the measurement range and precision are considered as key factors; the determined parameters include sampling air and hydrogen flow rate. In the final stage, all parameters are identified: a spray angle of 60°; salt bar composition of 78% NaCl, 22% MgCO3 and methylcellulose; a salt bar diameter of 12.5mm; liquefied petroleum gas (LPG) used as the inflammable gas; speed of gear device at 49mm/min; as well as LPG, sampling air, and hydrogen flow rates of 3.8l/min, 2l/min, and 200ml/min, respectively. Using one case of in-place testing of the air cleaning system in a waste plant and two applications in a nuclear power plant, we illustrate the applicability, stability, and continuity of the burning type sodium flame method for in-place filter testing.

Effective crop evapotranspiration measurement using time-domain reflectometry technique in a sub-humid region

The primary objective of this study was to evaluate the performance of the time-domain reflectometry (TDR) technique for daily evapotranspiration estimation of peanut and maize crop in a sub-humid region. Four independent methods were used to estimate crop evapotranspiration (ETc), namely, soil water balance budgeting approach, energy balance approach—(Bowen ratio), empirical methods approach, and Pan evaporation method. The soil water balance budgeting approach utilized the soil moisture measurement by gravimetric and TDR method. The empirical evapotranspiration methods such as combination approach (FAO-56 Penman–Monteith and Penman), temperature-based approach (Hargreaves–Samani), and radiation-based approach (Priestley–Taylor, Turc, Abetw) were used to estimate the reference evapotranspiration (ET0). The daily ETc determined by the FAO-56 Penman-Monteith, Priestley-Taylor, Turc, Pan evaporation, and Bowen ratio were found to be at par with the ET values derived from the soil water balance budget; while the methods Abetw, Penman, and Hargreaves-Samani were not found to be ideal for the determination of ETc. The study illustrates the in situ applicability of the TDR method in order to make it possible for a user to choose the best way for the optimum water consumption for a given crop in a sub-humid region. The study suggests that the FAO-56 Penman–Monteith, Turc, and Priestley–Taylor can be used for the determination of crop ETc using TDR in comparison to soil water balance budget.

Consumption of atmospheric CO2 via chemical weathering in the Yellow River basin: The Qinghai–Tibet Plateau is the main contributor to the high dissolved inorganic carbon in the Yellow River

The high HCO3− concentrations in the Yellow River (China) are generally believed to originate primarily from the carbonate-rich Loess Plateau as a result of carbonate weathering reactions that consume atmospheric CO2. We studied chemical weathering across the entire Yellow River basin in 2007 and 2009 and found that the amounts of CO2 consumption by carbonate and silicate weathering were 87.61×109mol/a and 10.70×109mol/a, respectively. As the source of water for the Yellow River, although the Qinghai–Tibet Plateau accounts for only 30% of the area of the basin, it has a strong leaching effect and contributes a majority (61%) of the atmospheric CO2 consumption of the entire basin and a majority of the riverine DIC flux (66%) to the ocean. As a result, the dissolved inorganic carbon (DIC) concentrations in this river are among the highest of the world's major rivers. In contrast, despite the abundant carbonate mineral content in the Loess Plateau, the high ratio of evaporation to precipitation (4.2) limits the weathering processes, and the low amount of runoff restricts the transport of weathering products, which results in a relatively low contribution (38%) to the basin-wide atmospheric CO2 consumption, which is much lower than was previously thought. The Qinghai–Tibet Plateau is the origin of the high levels of HCO3− in and acts as the main DIC contributor to the Yellow River.

Observational study on complementary relationship between pan evaporation and actual evapotranspiration and its variation with pan type

Abstract The pan evaporation process is essential to understanding the climate change of pan evaporation. To study the physical process of pan evaporation and its interactions with the surrounding environment, an elaborate pan evaporation experiment was carried out by means of micrometeorological method in the arid region of northwest China, in which hourly pan evaporation was measured by E601B, Class A and D20 pans, the local actual evapotranspiration was measured using eddy correlation system. Our results show that the pan water surface and the surrounding land surface constitute a significant non-uniformity of heat and moisture, and the non-uniformity energy exchange between them has an important influence on pan evaporation rate. As the environmental humidity changes, daily actual evapotranspiration and pan evaporation rates have a contradictory tendency, with the relationship between these two evaporations presenting a clear asymmetrical complementary behavior. In addition, a simple pan non-uniformity intensity index (IE) is defined as the ratio of pan evaporation to the Penman potential evaporation (LEppman) (IE = LEpan/LEppman). This index reflects the non-uniformity intensity between pan water and the surrounding land. Meanwhile, the comparison of complementary relationship corresponding to three types of pans shows that the degree of complementary relationship asymmetry linearly rises as the intensity of non-uniformity between pan and surrounding environment increases.

Curtailing Crop Production Risk in Dry Lands of Coimbatore District, Tamil Nadu

A systematic study was made to assess the variability and probability occurrence (initial and conditional) of rainfall at Coimbatore. Length of Growing Period (LGP) was also computed to plan dry land crop cultivation with minimum risk. LGP was computed by two different methods viz., weekly Moisture Availability Index (MAI) and weekly Rainfall /Potential Evaporation (R/PE) ratio. The mean weekly rainfall and PET data from 1961-2010 were used to compute LGP. The results indicated that for getting more than 25 mm with 50 per cent probability was possible from 42nd to 45th Standard Meteorological Week (SMW). The chance of receiving 20 mm rainfall per week with 50 per cent probability was observed from 39th to 49th week except in 48th week. The coefficient of variation was below 150 per cent from 16th to 23rd week and from 37th to 45th week. It showed that weekly rainfall during pre-monsoon and post monsoon season is highly dependable. LGP analysis shows that 77 days (37th to 47th week) was available as per MAI method and 91 days (37th to 49th week) period as per R/PE ratio.

Performance evaluation of a gas fired boiler in commercial dairy plant

Boiler is one of the most important components for dairy processing plant because which provide heating medium as steam at rate of required quantity with optimum quality .The present work is an account of Performance Evaluation Of A Gas Fired Boiler - A Case Study In commercial Dairy Industry . The study was aimed at assessing the operational performance of the gas fired boiler by evaluating the thermal efficiency and evaporation ratio. The analysis was carried out and found that the boiler having capacity of 501.6 kg steam production per hour at 6.8 kg/cm 2 with the help of natural gas consumption of 45.56 m 3 OR 27.33 kg. Evaporation ratio was obtained 18.35 per 1 kg of natural gas and 11 per 1 m3 of natural gas utilized. The thermal efficiency determined by direct method and indirect method was 72.75 per cent and 68.29, respectively. The cost for one kg steam production was obtained 1.866 Rupees.

Experimental study of fuel evaporation characteristics

Fuel evaporation characteristics are very important for the design of combustors. To quantitatively measure the fuel evaporation ratio of jet fuel in air cross flow, optical and physical measurement methods are proposed separately. The optical measurement method combines a high-speed camera and image-processing technologies, where as the physical measurement method applies the centrifugal force of a cyclone separator. The fuel evaporation ratio at different inlet conditions and different measurement cross-sections is analyzed separately for jet fuel in air cross flow. Finally, the experimental results of the physical method are compared with those of the optical method. The experimental results show that (1) the results of the optical measurement method are in good agreement with those of the physical measurement method, and these two methods can be used to quantitatively measure the fuel evaporation ratio at individual test cross-sections; (2) when other inlet parameters are the same, the fuel evaporation ratio at the test cross-section gradually increases with increasing inlet air Weber number; (3) when other inlet parameters are the same, the fuel evaporation ratio at the test cross-section gradually decreases with increasing momentum ratio; and (4) when inlet parameters are the same, the fuel evaporation ratio at the test cross-section increases sharply with increasing distance between the test cross-section and nozzle.

Small-sized biorefineries as strategy to add value to sugarcane bagasse

Small-sized biorefineries are not capital intensive and have lower transportation cost, lesser movements of liquid and solid streams, and lower heat transfer problems than high-sized ones. In this work, different scenarios were investigated in order to determine technical and economic viability of different processes to produce valuable products from sugarcane bagasse by small-sized biorefineries. Different alternatives were evaluated, as furfural and xylitol production from hemicelluloses, as well as energy generation and medium-density fibreboard (MDF) production from the residual solid after hemicelluloses hydrolysis. Experimental data obtained by the authors in previous works were used for pretreatment steps, and updated literature data was used for the other processes. A simplified kinetic model was developed for the extraction of xylose, and unit operations processes were selected and simulated. The most profitable option was determined for hemicelluloses use. In addition, costs and benefits that could be obtained exploiting the residual solid feedstock were estimated. The economic evaluation shows that recovery periods are extensive in both scenarios. However, optimization of different steps as liquid to solid ratio of pretreatment, evaporation, or fermentation, could represent attractive and innovative alternatives in order to reduce the recovery periods of capital costs.

Removal of polycyclic aromatic hydrocarbons (PAHs) from inorganic clay mineral: Bentonite.

There has been limited study of the removal of polycyclic aromatic hydrocarbons (PAHs) from inorganic clay minerals. Determining the amount of PAH removal is important in predicting their environmental fate. This study was carried out to the degradation and evaporation of PAHs from bentonite, which is an inorganic clay mineral. UV apparatus was designed specifically for the experiments. The impacts of temperature, UV, titanium dioxide (TiO2), and diethylamine (DEA) on PAH removal were determined. After 24h, 75 and 44% of ∑12 PAH in the bentonite were removed with and without UV rays, respectively. DEA was more effective as a photocatalyst than TiO2 during UV application. The ∑12 PAH removal ratio reached 88% with the addition of DEA to the bentonite. It was concluded that PAHs were photodegraded at high ratios when the bentonite samples were exposed to UV radiation in the presence of a photocatalyst. At the end of all the PAH removal applications, higher evaporation ratios were obtained for 3-ring compounds than for heavier ones. More than 60% of the amount of ∑12 PAH evaporated consisted of 3-ring compounds.

The influence of flow‐through saline gravel pit lakes on the hydrologic budget and hydrochemistry of a Mediterranean drainage basin

AbstractFlow‐through brackish gravel pit lakes near the Adriatic Coast of Emilia Romagna (Italy) in the Mediterranean have a large influence on the hydrologic budget of the watershed. Strong evaporation in combination with intense drainage of the low lying basins enhances groundwater inflow into the lake. Precipitation falling on the lakes is mixed with brackish/saline lake water causing the loss of freshwater. The gravel pit lakes are characterized by a high salinity (TDS = 4.6–12.3 g L−1) and high pH (8.5). Stable isotope data show that gravel pit lake water is fed by groundwater which is a mix of Apennine River water and (Holocene) Adriatic Seawater, subsequently enriched by evaporation. The slope of the local evaporation line is 5.4. Conservative tracer and water budget modeling shows that the final Cl concentration depends strongly on the ratio of evaporation to total inflow. Increasing drainage to compensate for sea level rise, subsidence or intense precipitation would enhance ground water flow into the lake and decrease Cl concentration while increasing evaporation would increase Cl concentration. Groundwater rich in dissolved trace elements flows into the gravel pit lakes that contains water with a higher pH and dissolved oxygen. Pit lake water remains enriched in some elements (e.g., Ba, Mo, Sb) and depleted in others (e.g., Fe, Ca, Zn, SO4) with respect to groundwater composition. The gravel pit lakes show limited eutrophication but the water quality should be monitored for trace elements (e.g., As) if they are to be used for recreational purposes.

Modeling evapotranspiration in a spring wheat from thermal radiometry: crop coefficients and E/T partitioning

Wheat is one of the crops occupying the largest areas in the world (218 million ha in 2013). Understanding the land–atmosphere energy exchanges over these croplands becomes important not only for agronomy but also for climatic and meteorological aspects. This study continues previous work on the estimation of actual evapotranspiration (ET) and the assessment of crop coefficients of sorghum, sunflower, or canola. Two variations of a simple two-source energy balance (STSEB) approach were used in combination with land surface temperature measurements to calculate hourly and daily values of surface fluxes and actual ET. An experiment was carried out during the spring season of 2014 in Las Tiesas experimental farm in Barrax, Spain. Soil and canopy temperature components together with meteorological variables and biophysical parameters were measured from planting to senescence. Comparison to lysimeter measurements showed calculation errors of ±0.11 mm h−1 and ±0.8 mm day−1 for hourly and daily ET values, respectively, whereas an underestimation no >4 % resulted from the entire campaign. Partition between soil and canopy components yielded a ratio of evaporation (E) to transpiration (T) of 36–64 %, respectively, for the total growing season. Dual crop coefficients were also calculated and compared to those proposed by FAO-56. Although separate E and T measurements were not available, similar results between the STSEB and FAO-56 models demonstrate the utility of the STSEB for investigating management strategies aimed at increasing crop water use efficiency.

Residue Mulch Effects on Potato Productivity and Irrigation and Nitrogen Economy in a Subtropical Environment

Depleting water resources in many regions of the world and increasing fertilizer nitrogen (N) cost necessitate efficient resource use. This is crucial in shallow-rooted crops like potato due to a great probability of water and N loss. In Indian Punjab, autumn potato experiences high temperature at planting time that causes poor growth and tuber yield. Mulching with crop residues provides favorable soil hydrothermal conditions that may enhance yield and economize irrigation and N use. This study examined the combined effects of residue mulch, irrigation, and N regimes on potato productivity in two soils in a subtropical environment of north-west India. Treatments included combinations of two mulch rates (0 and 6 t ha−1 rice residues) in main plots, three irrigation regimes (irrigation water to pan evaporation ratio of 2.0, 1.4, and 0.8 in the sandy loam and 2.0, 1.5, and 1.0 in the loamy sand) in subplots and four N rates (0, 135, 180, and 225 kg ha−1) in sub-subplots with three replications. Potato was planted in the second week of October with recommended doses of P2O5 and K2O and harvested in the last week of January. Tuber yield was higher in the sandy loam than in the loamy sand soil reflecting effects of available water capacity and inherent fertility. Mulching improved tuber yield by 22% on the sandy loam and by 31% on the loamy sand. Irrigation benefits were more in the sandy loam (20%) than in the loamy sand (14%). Nitrogen response was also greater in the sandy loam soil. Interactions between mulching and irrigation showed that yield gains from mulching were greater in less frequent irrigation regimes. For a given yield, mulching saved 90–100 mm of irrigation water. Mulching benefits were also greater at low N regimes, demonstrating a saving of 90 kg N ha−1 for a given yield. Mulching and N enhanced water productivity (WP), and these effects were greater in less frequent irrigations. Mulching effects on tuber yield, irrigation, and N economy are attributed to its effects on moderation of soil temperature and reduction in soil water evaporation.

Isothermal Evaporation Process Simulation Using the Pitzer Model for the Quinary System LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K

In this study, the Pitzer thermodynamic model for solid-liquid equilibria in the quinary system LiCl–NaCl–KCl–SrCl2–H2O at 298.15 K was constructed by selecting the proper parameters for the subsystems in the literature. The solubility data of the systems NaCl–SrCl2–H2O, KCl–SrCl2–H2O, LiCl–SrCl2–H2O, and NaCl–KCl–SrCl2–H2O were used to evaluate the model. Good agreement between the experimental and calculated solubilities shows that the model is reliable. The Pitzer model for the quinary system at 298.15 K was then used to calculate the component solubilities and conduct computer simulation of isothermal evaporation of the mother liquor for the oilfield brine from Nanyishan district in the Qaidam Basin. The evaporation-crystallization path and sequence of salt precipitation, change in concentration and precipitation of lithium, sodium, potassium, and strontium, and water activities during the evaporation process were demonstrated. The salts precipitated from the brine in the order : KCl, NaCl, SrCl2∙6H2O, SrCl2∙2H2O, and LiCl∙H2O. The entire evaporation process may be divided into six stages. In each stage the variation trends for the relationships between ion concentrations or water activities and the evaporation ratio are different. This result of the simulation of brines can be used as a theoretical reference for comprehensive exploitation and utilization of this type ofmore » brine resources.« less

Water use and crop coefficient of the wheat–maize strip intercropping system for an arid region in northwestern China

Relay strip intercropping of spring wheat and maize is practiced on a large scale in arid regions of northwestern China. In this study, a field experiment was carried out during 2012 and 2013 growing seasons to examine water use and crop coefficient of this system in an arid environment. The experiment comprised three treatments: sole-cropped wheat, sole-cropped maize, and wheat–maize intercropping. The grain yields of both intercropped wheat and maize were enhanced by intercropping. The gross economic profit for wheat–maize intercropping was 16.4% lower than that of sole maize and 95.4% higher than that of sole wheat. The overall land use efficiency was improved by intercropping. The time course of leaf area index in intercropping had the similar trends to those in sole crops with relatively low values, which never exceeded 3.0m2m−2 throughout both growing seasons. Compared to weighted means of the sole-cropping systems, wheat–maize intercropping used 26% and 24% more water in 2012 and 2013, respectively. The water-use efficiency of intercropping was nearly the same as the weighted means of the sole crops. Due to the incomplete groundcover in intercropping plots, more water was consumed as soil evaporation. Averaged over two seasons, the ratio of soil evaporation to actual evapotranspiration was 33.4, 20.7 and 24.1% for intercropping system, sole-cropped wheat and sole-cropped maize, respectively. Crop coefficient (Kc) of sole-cropped wheat was 0.19±0.02, 1.05±0.07, and 0.42±0.09 at the initial, mid and late season in two seasons, respectively. Kc value of the sole-cropped maize was 0.22±0.03, 1.10±0.06 and 0.60±0.02 at the initial, mid and late season, respectively. The Kc values of the wheat–maize intercropping system varied in 0.21±0.03, 0.89±0.05, and 0.78±0.06 at the initial, middle and late wheat growing season, and in 0.85±0.03 and 0.61±0.01 at the middle and late maize growing season, respectively. Therefore, longer growing season and incomplete ground cover are the main factors that resulted in higher water use for wheat–maize intercropping compared to sole crops. Results of this study can help to improve the irrigation efficiency for the wheat–maize strip intercropping system.

Model Spin-Up Behavior for Wet and Dry Basins: A Case Study Using the Xinanjiang Model

Model spin-up is an adjustment process where its internal stores move from an initial state of unusual conditions to one of equilibrium. Model outputs during this spin-up process are often unrealistic and misleading. This study investigates some primary factors affecting spin-up time using the Xinanjiang model for 22 river basins throughout the United States. A 10-year recursive simulation with three data sets indicates that time required for model equilibrium is not only a function of initial conditions, but also is affected by input data sets (precipitation and evaporation). The model requires less time to be equilibrated under wetter initial conditions (lowest under saturated initial condition). Moreover, model spin-up time shows distinct variations with the dryness of the input data sets. Analysis suggests that wet basins (ratio of evaporation over precipitation <0.9) require less time (55 days) for model equilibrium in comparison to that of dry basins (298 days). The spin-up time displayed an exponential relationship with the basin aridity index (r2 = 0.85). This relationship could provide a way to predict the maximum model spin-up time using the precipitation and evaporation information only. Predicting maximum model spin-up time based on this relationship could be valuable to reduce uncertainty, particularly under data scarce situations.

Inhibiting evaporation of heavy metal by controlling its chemical speciation in MSWI fly ash

Abstract The heavy metal (HM) evaporation in the thermal treatment of fly ash (FA) from municipal solid waste incineration (MSWI) has attracted considerable attention because the inhalation of or skin exposure to heavy metal raises human health risks. In this study, the washing and chemical treatments of FA were performed to inhibit the evaporation of HM (Zn, Pb and Cd) followed by a volatilization test of the pretreated FA at a temperature of up to 1000 °C. The results indicate that the evaporation behavior of HMs in fly ash was significantly affected by chemical speciation. The evaporation ratios of HMs with different speciations decreased in the order of acid soluble (F1) > reducible (F2) > oxidizable (F3) > residual (F4). The washing pretreatment process on fly ash would largely inhibit the evaporation of HMs by removing most of the metal chlorides, which are the dominant component of the F1 fraction. Meanwhile, the fly ash after phosphate chemical pretreatment has the least evaporation via converting the F1 fraction into the chemically stable F4 fraction. Therefore, the controllable formation of chemical speciation could effectively inhibit HM evaporation in fly ash.

Integrating liquid fraction of pig manure in the composting process for nutrient recovery and water re-use

Composting of solid fraction of swine manure is a usual practice in most farms in order to obtain a fertilizer of better quality. Due to the negative hydric balance of the composting process, watering the composting material is necessary, what may be carried out with liquid fraction of pig manure. In this way, substantial amounts of liquid fraction can be treated by composting, allowing the recovering the nutrients and reducing the volumes to be transported to the more distant crop fields or subjected to further treatment. Thus, the main objective of this research was to study the treatment of liquid fraction of pig manure by co-composting with solid fraction of pig manure and other solid biowaste generated in rural areas. The present research is part of a project to find an integral solution for pig manure consisting of nutrient recovery through compost production and water re-use after biological purification in constructed wetlands. In accordance with the European waste management hierarchy, sustainable and low cost cleaner technologies aiming at resource recovery must be developed as an alternative to conventional technologies applied to the treatment of pig manure. This paper presents the results of composting of liquid fraction of fresh manure, which is conceived at the same time as a pig wastewater pre-treatment, wastewater volume reduction and a nutrient recovery system. Two 30 m3 turned windrows were constituted with solid fraction of pig manure and Populus sp. wood chips as bulking material at volume ratios of 1:1 and 1:2 and watered intensely with liquid fraction whilst thermophilic temperatures were maintained. Subsequently, both windrows were divided and the new windrows each received the same quantity of a different organic waste (solid fraction of pig manure, sawdust and grape bagasse), being watered with liquid fraction for a further 30 days. Stabilised composts with a nitrogen content ranging from 1.8 to 2.0% and a carbon to nitrogen ratio from 14.0 to 18.8 were obtained. Water balances showed evaporation rates ranging from 14 to 76 L/t total solids·d and overall evaporation ratios from 1 to 2.7 m3/t total solids, referred to dry matter of solid waste. While the reduction of liquid fraction volume ranged from 58 to 88% (depending on the watering rate), mass reduction of pollutants reached approximately 90% of total Kjeldahl nitrogen, ammonium and suspended solids. In comparison with traditional composting processes of solid fraction, our results show that huge amounts of liquid fraction can be treated by co-composting with solid fraction and other solid wastes. Integrating the liquid fraction of pig manure in the composting process has improved the compost quality and has reduced the pollutant load in the remaining liquid fraction, which makes possible an advanced treatment in constructed wetlands in order to reach the necessary water quality to be recycled or even to discharge in natural water bodies. In this way, both composting and constructed wetland systems can offer an integral solution for the recovery of water and fertilizer elements contained in pig manure and diverse locally generated solid wastes. However, in spite of these benefits, more research focussing on nitrogen balances, ammonia volatilisation and greenhouse emissions will be of great interest.

Quantitative estimation of land surface evapotranspiration in Taiwan based on MODIS data

Land surface evapotranspiration (ET) determines the local and regional water-heat balances. Accurate estimation of regional surface ET provides a scientific basis for the formulation and implementation of water conservation programs. This study set up a table of the momentum roughness length and zero-plane displacement related with land cover and an empirical relationship between land surface temperature and air temperature. A revised quantitative remote sensing ET model, the SEBS-Taiwan model, was developed. Based on Moderate Resolution Imaging Spectroradiometer (MODIS) data, SEBS-Taiwan was used to simulate and evaluate the typical actual daily ET values in different seasons of 2002 and 2003 in Taiwan. SEBS-Taiwan generally performed well and could accurately simulate the actual daily ET. The simulated daily ET values matched the observed values satisfactorily. The results indicate that the net regional solar radiation, evaporation ratio, and surface ET values for the whole area of Taiwan are larger in summer than in spring, and larger in autumn than in winter. The results also show that the regional average daily ET values of 2002 are a little higher than those of 2003. Through analysis of the ET values from different types of land cover, we found that forest has the largest ET value, while water areas, bare land, and urban areas have the lowest ET values. Generally, the Northern Taiwan area, including Ilan County, Nantou County, and Hualien County, has higher ET values, while other cities, such as Chiayi, Taichung, and Tainan, have lower ET values.

Effects of different vegetation restoration on soil water storage and water balance in the Chinese Loess Plateau

Large-scale vegetation restoration in the Chinese Loess Plateau has been initiated by the central government over the past decades to control soil and water loss. However, no guidelines are followed in plant species selection for vegetation restoration. We examined the effects of planting Pinus tabuliformis, Robinia pseudoacacia, Caragana korshinskii, and Hippophae rhamnoides on soil water dynamics and water stresses by measuring canopy interception, soil evaporation, plant transpiration, and surface runoff from May to September of 2009–2013 in the semi-arid loess hilly area. Results showed the following: (1) Water loss exceeded precipitation in most months during the growing seasons. The amount of soil water storage decreased within a 100cm depth in all land cover types from 2009 to 2013. Land cover examination showed that the slope of the decline trend of soil water storage for C. korshinskii was much lower than that of the other land cover types. However, P. tabuliformis exhibited the biggest decline slope among the four land cover types. (2) The ratio of actual evapotranspiration (ET) and pan evaporation (Ep) was low for all land cover types during the study period. The ET/Ep ratios followed the order (from highest to lowest) C. korshinskii>R. pseudoacacia>H. rhamnoides>P. tabuliformis. When the monthly rainfall amount was lower than 50mm, H. rhamnoides showed the lowest ET/Ep ratio among the four land cover types, but high ET/Ep ratio was observed in H. rhamnoides with large rainfall amount (>70mm). The current study suggested that P. tabuliformis plantation should not be the first choice for vegetation restoration in such a semiarid loess hilly area. H. rhamnoides is suitable for afforestation in areas with high levels of rainfall. C. korshinskii and R. pseudoacacia are highly recommended for vegetation restoration.