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1.
Aquatic ecosystems are threatened by increasing variability in the hydrologic responses. In particular, the health of river ecosystems in steeply sloping watersheds is aggravated due to soil erosion and stream depletion during dry periods. This study suggested and assessed a method to improve the adaptation ability of a river system in a steep watershed. For this, this study calibrated soil and water assessment tool (SWAT) for runoff and sediment, and quantified the changes in hydrologic responses such as groundwater recharge rate soil erosion and baseflow according to two scenarios for adjustment of the watershed slope (steep to mild). Here, one scenario was set by three measured slopes, and the other was set by fixing the entire watershed slopes with 5 %. Moreover, SWAT and web-based hydrograph analysis tool (WHAT) models were applied to estimate groundwater recharge, soil erosion, and baseflow in the Haean-myeon watershed in South Korea. The results show that the reduction of watershed slope increased groundwater recharge and baseflow, and decreased sediment. Specifically, groundwater recharge rate was increased from 257.10 to 364.60 mm, baseflow was increased from 0.86 to 1.19 m3/s, and sediment was decreased from 194.6 to 58.1 kg/km2. Based on these results, the suggested method will positively contribute to aquatic ecosystems and farming environments in a steeply sloping watershed due to improvements in the quantity and quality of river water.  相似文献   

2.
The effect of land use change on drying streams was evaluated using a grid-based continuous hydrological model (PGA-CC). For a drying stream-progressed watershed (398.8 km2), the model was calibrated and validated using 7 years (2005–2011) of streamflow data at the watershed outlet with an average Nash–Sutcliffe model efficiency of 0.71. Based on the model simulation results for 36 years (1976 to 2011), both land use change and climate change decreased the 10-day minimum flow by 0.16 m3/s and increased the day counts below the annual average by 40.6 days/year. These changes resulted from the 8.7 % increase in urban area, 1.43-fold increase in groundwater use, and 1.1 °C temperature increase during the 36-year period. From the distributed results of the model, we identified the drying stream location and progression. The spring and winter seasons were relatively strongly affected, and drying streams were identified in more urbanized areas with greater groundwater use.  相似文献   

3.
An evaluation of the nitrogen pollution load potential (NPLP) arising from several sewage treatment systems in the Tedori River Alluvial Fan Area was evaluated by determining the removal percentage of nitrogen as a result of sewage treatment and amounts of nitrogen lost from the different treatment systems. These data were applied to the entire area resulting in an estimated total NPLP of 734 t year−1 (103 kg year−1), of which 548 t year−1 discharges into the Japan Sea and so does not contribute to the pollution of the environment considered here. The residual 186 t year−1 of the NPLP has a high probability of causing groundwater or downstream pollution, with 58% of the NPLP being contributed from septic tanks not connected to public sewage systems. Rural sewage system accounted for about 18% of the NPLP. Material directly flowing into the middle stream of the Tedori River together with sewage water from small companies and untreated sewage water from local family dwellings made up about 3–12% of the NPLP. To improve water quality due to sewage effluent, it is essential to increase the number of connections to public sewage systems from septic tanks.  相似文献   

4.
The Total Maximum Daily Load (TMDL) program is an integrated process of watershed assessment and management to address surface water quality impairment. The management of organic contaminants and nutrients is a primary concern in conserving surface water bodies. Watershed-scale pollutant loads simulation can assist stakeholders and watershed planners in making decisions on immediate and long-term land use schemes to improve water quality. However, the behavior of contaminants in a watershed needs to be characterized prior to such model applications. The objectives of this study were to characterize point and nonpoint pollutants runoff at a watershed scale and to develop a Pollutant Load Calculation Model (PLCM), which facilitates the estimation of pollutant delivery to a watershed outlet. The developed model was applied for the six sub-watersheds of the Saemangeum estuarine watershed in Korea, where a large tidal reclamation project has been underway. Two years stream flow and water quality data were used for the model calibration, while 1 year data were utilized for the model validation. The model calibration resulted in the R 2 values of 0.58, 0.53, and 0.35 for BOD, TN, and TP, respectively. Overall performance for the validation period was similar with that for the calibration period although the R 2 values were slightly decreased. The PLCM tends to substantially under or overestimate delivery pollutants loads during the summer rainy seasons when most rainfall events occur. This is probably because once-a-month-measured water quality data, which might not represent appropriately monthly water quality, particularly, for rainy seasons, were used for the loads calculation. Thus, more frequently monitored water quality data should be used for the delivery loads estimation at least for a rainy season in order to improve the PLCM performance. Nevertheless, the developed model took the pollutant reduction process into account, which is not allowed with the conventional unit loading method, and furthermore temporal variations of pollutant loads based on stream flows were also incorporated into the pollutant loads estimation. The developed PLCM can be a useful tool to assess pollutants delivery loads at a watershed scale and thus assist decision makers in developing watershed pollution management schemes.  相似文献   

5.
The objective of this research was to investigate the critical water content (θ c) and water stress coefficient (K s) of soybean plant under deficit irrigation. This research was conducted in a plastic house at the University of Lampung, Sumatra in Indonesia from June to September 2000. The water deficit levels were 0–20%, 20–40%, 40–60%, 60–80%, and 80–100% of available water (AW) deficit, arranged in Randomized Completely Block (RCB) design with four replications. The results showed that the soybean plant started to experience stress from week IV within 40–60% of AW deficit. The fraction of total available water (TAW) that the crop can extract from the root zone without suffering water stress (p) was 0.5 and θc was 0.305 m3 m−3. The values of K s at p=0.5 were 0.78, 0.86, 0.78, and 0.71 from week IV to week VII, respectively. The optimum yield of soybean plant with the highest yield efficiency was reached at 40–60% of AW deficit with an average K s value of 0.78; this level of deficit irrigation could conserve about 10% of the irrigation. The optimum yield of soybean plant was 7.9 g/pot and crop water requirement was 372 mm.  相似文献   

6.
A distributed hydro-environmental model is developed that achieves detailed analysis of the movement of water at a field-plot-scale resolution in a mesoscale watershed including lowland areas where, especially for agricultures, it is an essential need to get rid of redundant groundwater by drainage facilities such as rivers, canals and/or underdrains. For this, the problem geometry is meshed with unstructured cells of triangular shape. Profile of a column cell is zoned into two: surface zone and groundwater zone in which water movement is represented by combined tank and soil moisture sub-models, and well-defined two-dimensional unconfined shallow groundwater flow sub-model, respectively. The top-two sub-models serve to evaluate evapotranspiration, infiltration, soil water content, lateral surface water flow, and vertical percolation. The vertical percolation so evaluated is given as longitudinal recharge to the bottom sub-model for computing groundwater flow. Surface water–groundwater interactions through beds and stream-banks of perennial and ephemeral canals are considered by treating the canal courses as internal boundaries in the groundwater flow model. The finite volume method (FVM) that allows of unstructured mesh and produces conservative solutions is employed for groundwater flow computation. The model developed is applied to an actual watershed which includes a low-lying paddy area to quantify the hydrological impact of land-use management practices over a period of 29 years in which the farmland consolidation project was implemented and part of the paddy fields were converted to upland crop fields and housing lands. From the results obtained, it is concluded that the model presently developed lends itself to water—as well as land-use management practices.  相似文献   

7.
This study aims to assess the nitrogen contamination of groundwater in paddy and upland fields. A reactive chemical transport model PHREEQC and a variable saturated groundwater flow and transport model FEMWATER were used to evaluate the vertical transport of nitrogen compound in various soil types of paddy and upland. The shallow groundwater quality monitoring data of 2003, 2006, 2009 in the Choushui river alluvial fan, the major agriculture production area in Taiwan, were applied to support the validity of the numerical simulation findings. Results from PHREEQC and FEMWATER simulations showed that the organic-rich impermeable plow sole layer underneath the muddy layer of rice paddy can effectively reduce NO3 − and N2 to NH4 + and retard the movement of NH4 +. However, in the upland field which has no plow sole layer, the NH4 + can move easily to the shallow aquifer and contaminate the groundwater. The spatiotemporal distribution of NO3 −–N and NH4 +–N in the Choushui river alluvial fan revealed that high nitrate–N contamination areas were located mainly in the upland field of the proximal fan, where the granular unconfined aquifer was vulnerable to surface contaminants. Moreover, the unconfined nature of the aquifer allows the oxidization of NH4 + to NO3 − and accelerates the plume movement. High ammonium–N concentration areas were mostly dispersed in the distal-fan area where upland planting and aquacultural farming were prevailed. The high NH4 +–N found in the northern Choushui river alluvial fan was attributed to the alternative planting of rice and upland crops, and the plow sole layer was broken to maintain the quick drainage upland crop needs.  相似文献   

8.
The simulated streamflow from Thiessen average rainfall (T) and spatially distributed rainfall (R) may be significantly different from each other. To identify the hydrologic effects quantitatively, the grid-based kinematic wave storm runoff model was adopted. The model predicts temporal and spatial variations of surface and subsurface flow at each cell by calculating the water balance, and routes the streamflow to the outlet. The model was tested at the Yeoncheondam watershed (1,875 km2), one third of which belongs to North Korea. The watershed is elongated to north and south directions crossing the border. Four rain gauges cover the watershed within the territory of South Korea, while no records from North Korea are given. The simulated results showed the large differences in runoff volume and peak flow rates between T and R when rain moves in a north to south direction. The simulated results of east-to-west-direction storms showed little difference in the hydrographs. The hydrograph was strongly affected by the spatial variations of the rainfall moving along the stream of the watershed.  相似文献   

9.
The water balance and groundwater dynamics due to surface–groundwater interactions for watershed health assessment were investigated for the Han River basin (34,148 km2) of South Korea using the Soil and Water Assessment Tool (SWAT). The model was established considering 4 multipurpose dams and 3 multifunction weirs. The SWAT was spatially calibrated and validated using daily observed inflows for the dam (2005–2014) and weir (2012–2014) as well as evapotranspiration, soil moisture, and groundwater level data (2009–2013). The simulation results revealed the impact of surface–groundwater exchange fluxes on the water balance and baseflow by evaluating the vertical water budget and horizontal water transfer. Evapotranspiration in the surface and return flows from the shallow aquifer for the dry season was estimated to be 29 and 10% higher than for the wet season, respectively. Percolation’s role was also significant, providing approximately 24% of the annual groundwater recharge to shallow aquifers in the rainy season. On average, the February to August period (A) was characterized by a net flux of infiltration into the groundwater. For the September to January period (B), the proportion of groundwater flow into the river of the basin was nearly balanced by a slight increase in surface water infiltration. During period A of average surface water infiltration into the groundwater, the net groundwater recharge was positive and up to 20% of the infiltration during this period resulted from groundwater recharge. These results showed that groundwater recharge is strongly affected by the surface water and groundwater interactions.  相似文献   

10.
This study of a water cycle was conducted in an evergreen forest located in the Mekong River Basin in central Cambodia. At the observation site, we measured the dynamics of the spatial distribution of groundwater levels. The groundwater movement was analyzed two-dimensionally using boundary conditions and parameters that had been observed in the field. The climate in the research area is dominated by two seasons, which occur annually: a rainy and a dry season. The groundwater levels are generally high during the rainy season and low during the dry season. Groundwater levels were measured along a stream, which flowed through the study site. The streambed was visible at the head of the stream in January. At the next downriver well point, the streambed appeared in March. Finally, it became visible at all well points in April, meaning that surface runoff had disappeared temporarily and instead flowed underground during the ensuing dry period. Groundwater levels of the studied lateral flow perpendicular to the stream that seeped and infiltrated into the stream were 1.2–2.5 m deep (in April), which was the lowest level recorded for the year. During that period, the depth of the groundwater of the studied lateral flow fell by as much as 56 mm per month. In addition, the lateral flow groundwater infiltrated into groundwater of the stream during that period. The groundwater level fluctuation was estimated based on a two-dimensional analysis of lateral flow perpendicular to the stream using a numerical simulation model with soil physical parameters and observed boundary conditions. The observations of ground water fluctuations were well reproduced. Deep seepage of groundwater was estimated using a uniform boundary condition that allowed efflux through the bottom, estimated as being approximately 30 mm per year. The simulated deep seepage rate was considered plausible considering other hydrological components such as soil water storage fluctuation.  相似文献   

11.
Insufficient puddling with inappropriate implements or imprecise time/intensity may alter saturated water flow in paddy soil spatially or temporary due to change in aggregate size distribution, dry bulk density, saturated hydraulic conductivity, and percolation rate of the soil. In this study, spatial variability of saturated hydraulic conductivity (K s), a key parameter of the saturated water flow, in Fuchu Honmachi paddy plot (100 m × 28 m) was characterized based on dielectric or ADR dry bulk density (ρb-ADR) with help of non-similar media concept (NSMC) and geostatistics model to meet its correlation to subsurface percolation. A 100 cc core and an ADR data were sampled from each sub-plot (7 m × 7.5 m), and then were used for measuring and predicting ρb and K s. The predicted data agreed with the measured ones, in which they fitted well the x = y line with RMSE of 0.029 cm3 cm−3 (R 2 = 0.68), 0.027 g cm−3 (R 2 = 0.71) (ρb), and 0.098 cm d−1 (R 2 = 0.45) for θ, ρb, and K s, respectively. The predicted ρb and K s had similar trend in spatial variability to the measured ones particularly within the distance of 46.3–51.9 m and 26.2–27.9 m, respectively. The spatial variability of the predicted K s coincided to that of the subsurface percolation rate, in which they had similar distance of dependence. The results indicated that the presenting method can be reasonably accepted.  相似文献   

12.
The effects of vegetable type, vegetable dimensions, and solar drier load on dehydration rate; and texture, color, water activity, and carotene content of solar-dried carrots, sweet potatoes, and collard greens were studied. Mean dehydration rates (moisture loss,%/hr) for solar dried loads of 430 g/m2 and 715 g/m2 were 3.3 ± 0.30% and 3.8 ± 0.20% for carrots and sweet potatoes, respectively. Loads of 360 g/m2 and 465 g/m2 of collard greens had dehydration rates of 6.3 ± 0.10% moisture loss per hr. The results showed that vegetable type accounted for significant differences (p < 0.01) in dehydration rate, and beta-carotene content. Vegetable dimensions affected (p < 0.05) water activity. Solar drier load affected water activity (p < 0.01), and hue angle (p < 0.05). Beta-carotene contents (dry basis) of dehydrated carrot, sweet potato, and collard treatments were 10.9–17.4%, 7.6–9.8%, and 11.9–21.5%, respectively. Among the carrot treatments, the 5-mm thick slices packed at a load of 715 g/m2 contained the highest beta-carotene (17.4%, dry basis) and vitamin A activity (362 IU/g, dry basis), and good physical properties. For collard greens, the 2-cm and 3-cm wide strips packed at 360 g/m2 loads had the best combinations of high beta-carotene (21.5% and 17.2%, dry basis, respectively), vitamin A activity (357.2 and 293.1 IU/g, dry basis, respectively), and optimal color, texture, and water activity. Beta-carotene losses due to solar dehydration were 48.9–67.5%, 4.0–5.8%, and 1.9–19.8% (dry basis) in carrots, sweet potato and collard greens, respectively.  相似文献   

13.
The presence of arsenic in irrigation water and in paddy field soil were investigated to assess the accumulation of arsenic and its distribution in the various parts (root, straw, husk, and grain) of rice plant from an arsenic effected area of West Bengal. Results showed that the level of arsenic in irrigation water (0.05–0.70 mg l−1) was much above the WHO recommended arsenic limit of 0.01 mg l−1 for drinking water. The paddy soil gets contaminated from the irrigation water and thus enhancing the bioaccumulation of arsenic in rice plants. The total soil arsenic concentrations ranged from 1.34 to 14.09 mg kg−1. Soil organic carbon showed positive correlation with arsenic accumulation in rice plant, while soil pH showed strong negative correlation. Higher accumulation of arsenic was noticed in the root (6.92 ± 0.241–28.63 ± 0.225 mg kg−1) as compared to the straw (1.18 ± 0.002–2.13 ± 0.009 mg kg−1), husk (0.40 ± 0.004–1.05 ± 0.006 mg kg−1), and grain (0.16 ± 0.001–0.58 ± 0.003 mg kg−1) parts of the rice plant. However, the accumulation of arsenic in the rice grain of all the studied samples was found to be between 0.16 ± 0.001 and 0.58 ± 0.003 mg kg−1 dry weights of arsenic, which did not exceed the permissible limit in rice (1.0 mg kg−1 according to WHO recommendation). Two rice plant varieties, one high yielding (Red Minikit) and another local (Megi) had been chosen for the study of arsenic translocation. Higher translocation of arsenic was seen in the high yielding variety (0.194–0.393) compared to that by the local rice variety (0.099–0.161). An appreciable high efficiency in translocation of arsenic from shoot to grain (0.099–0.393) was observed in both the rice varieties compared to the translocation from root to shoot (0.040–0.108).  相似文献   

14.
The utility of short-wavelength near-infrared spectroscopy (over the wavelength region 750–950 nm), used in a partial transmittance optical geometry, was assessed as a means of estimating the dry matter concentration of potato tubers. The sampling optics did not involve contact with the sample, and could be used on a moving stream of product. A prediction accuracy of R 2 (correlation coefficient of determination) of 0.85 with a root mean square error of prediction (RMSEP) of 1.52% for intact, whole tubers and R 2 = 0.95 and RMSEP = 0.50% for sliced tubers was achieved. We conclude that short-wavelength near-infrared technology using a partial transmittance optical sampling geometry can be a useful tool for rapid assessment of tuber dry matter concentration prior to processing.  相似文献   

15.

Background  

Bi-directional flow of nutrients between marine and terrestrial ecosystems can provide essential resources that structure communities in transitional habitats. On the Pacific coast of North America, anadromous salmon (Oncorhynchus spp.) constitute a dominant nutrient subsidy to aquatic habitats and riparian vegetation, although the contribution to terrestrial habitats is not well established. We use a dual isotope approach of δ15N and δ13C to test for the contribution of salmon nutrients to multiple trophic levels of litter-based terrestrial invertebrates below and above waterfalls that act as a barrier to salmon migration on two watersheds in coastal British Columbia.  相似文献   

16.
A grid-based, KIneMatic wave STOrm Runoff Model (KIMSTORM) is described. The model adopts the single flow-path algorithm and routes the water balance during the storm period. Manning’s roughness coefficient adjustment function of the paddy cell was applied to simulate the flood mitigation effect of the paddy fields for the grid-based, distributed rainfall-runoff modeling. The model was tested in 2296 km2 dam watershed in South Korea using six typhoon storm events occurring between 2000 and 2007 with 500 m spatial resolution, and the results were tested through the automatic model evaluation functions in the model. The average values of the Nash–Sutcliffe model efficiency (ME), the volume conservation index (VCI), the relative error of peak runoff rate (EQp), and the absolute error of peak runoff (ETp) were 0.974, 1.016, 0.019, and 0.45 h for calibrated storm events and 0.975, 0.951, 0.029, and 0.50 h for verified storm events, respectively. In the simulation of the flood mitigation effect of the paddy fields, the average values of the percentage changes for peak runoff, total runoff volume, and time to peak runoff were only −1.95, −0.93, and 0.19%, respectively.  相似文献   

17.
Long-term changes (1974–2007) in the nitrogen pollution load potential (NPLP) arising from sewage treatment water were assessed in the Tedori River Alluvial Fan Area of Japan. The total NPLP from sewage treatment systems (STS) during the 34 year period was 439 t (103 kg) year−1 from about 260,000 users in 1974 increasing to a peak of 793 t year−1 in 1992 from about 363,000 users, and then decreasing to 676 t year−1 from about 400,000 users in 2007. The NPLP outflow into the area increased from 356 t year−1 in 1974 to a peak of 596 t year−1 in 1985 followed by a rapid decrease to 98 t year−1 in 2007. The NPLP outflow from the public STS to the Japan Sea began in 1979 and rapidly increased to 575 t year−1 in 2007 from about 362,000 users. This represents 85.5% of the total NPLP. The NPLP from septic tanks in the area was 356 t year−1 from about 107,000 users in 1974 gradually increasing to a peak of 587 t year−1 from about 177,000 users in 1985 before rapidly decreasing to 60 t year−1 from about 15,000 users in 2007. Although the current NPLP is about 98 t year−1 in the study area, the average NPLP during 34 years was very different at 424 t year−1. NPLP assessments affecting groundwater and closed water bodies should consider long-term processes of nitrogen pollution from STS over time periods compatible with the residence time of the receiving waters.  相似文献   

18.
A cell-based distributed watershed model is developed which enables us to simulate the hydrological and hydraulic aspects of the watershed in a refined fashion. With three-zoned cell profiling, the model is composed of three sub-models; tank model for a surface water zone, soil moisture model for a surface soil zone, and unconfined shallow groundwater flow model for a subsurface zone. Inclusion of the soil moisture sub-model modified to reroute the infiltration, routed from the tank sub-model, into the return flow and the groundwater recharge features the model. The groundwater flow sub-model, numerically approximated by use of the finite volume method and the implicit time-marching scheme, considers a network of on-farm drainage canals as internal boundaries, which is an essential need for modeling the watershed including farmlands. Cascade-linking of the three sub-models in a cell and assembling of all the cells over the entire watershed domain provides the global equations system to be solved. Applicability of the model is demonstrated with its practical application to a real watershed in that paddy and upland crop fields take great part of the land-use practice. It is then indicated in a quantified manner that rice farming significantly contribute as a major groundwater recharger in an irrigation period to fostering and conservation of regional water resources. Along with appropriately profiling a cell, the model is so versatile and tough that it can be applied without difficulty to a watershed of diverse terrains and land-uses and the computations can stably be carried out. It is thus concluded that the model presently developed could be a powerful “watershed simulator” to investigate and assess the time-varying hydro-environmental properties of a watershed while separating and integrating the hydrological and hydraulic components of particular importance.  相似文献   

19.
A study was undertaken to estimate the sediment yield of the Karso watershed of Hazaribagh, Jharkhand State, India using modified universal soil loss equation (MUSLE), remote sensing (RS) and geographic information system (GIS) techniques. The runoff factor of MUSLE was computed using the measured values of runoff and peak rate of runoff at outlet of the watershed. The topographic factor (LS) was determined using GIS while crop management factor (C) was determined from land use/land cover data, obtained from RS and field survey. The conservation practice factor (P) was obtained from the literature. Sediment yield at the outlet of the study watershed was simulated for 345 rainfall events spread over a period of 1996–2001 and validated with the measured values. Nash–Sutcliffe simulation model efficiency of 0.8 and high value of coefficient of determination (0.83) indicated that MUSLE model estimated sediment yield satisfactorily.  相似文献   

20.
Long-term simulation using the distributed hydro-environmental watershed model is efficacious for assessing irrigation impacts on hydrological cycle in detail and for implementing watershed management successfully. In this article, the previously developed hydro-environmental watershed model (HEWM-1) is improved in the water exchange process caused by surface water-groundwater interaction via drainage canals and/or underdrains. The time-varying stream flow in canals is described by the complete one-dimensional shallow water equations in a newly introduced submodel, the open channel flow submodel. This submodel coordinates with the other submodels: the tank, soil moisture and groundwater flow submodels which are interlinked in a cascade manner. The improved model (HEWM-2) is applied to an agricultural watershed covering an area from an alluvial fan onto a nearly level alluvial plain, to be validated. The simulation by HEWM-2 is informative for identifying whether any drainage canal is gaining or losing water in relation to groundwater level. It could thus provide useful information for conserving a complex network of drainage canals which also functions as a passage for aquatic animals like fishes.  相似文献   

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