Influence of paddy rice terraces on soil erosion of a small watershed in a hilly area of Northern Vietnam

Soil erosion is the main cause of soil degradation in northern Vietnam. In this study, soil erosion was measured in 2 m² field plots, a 19.1-ha sub-watershed, and a 248.9-ha main watershed in Tam Quan commune, Tam Duong district, northern Vietnam during 2 years, i.e., 2004–2005. The main watershed includes lowland paddy fields, and is representative for watersheds in the northern Vietnamese landscape. Soil erosion was measured for eight events, at all the three scales to increase our understanding of erosional processes and to assess the effects of paddy fields within the main watershed. The results show that total discharge and sediment yield in both sub-watershed and main watershed were much lower than those in the field plots. Total discharge per unit area in the main watershed was higher than in the sub-watershed, because during the growing season, the paddies are filled with water and any rainfall on them therefore becomes runoff. Sediment yield in the main watershed fluctuated, depending on the soil erosion contribution from many sub-watersheds. Annual rainfalls in 2004 and 2005 were 1,172 and 1,560 mm, respectively, resulting in corresponding total discharges of 54 and 332 mm and total soil losses of 163 and 1,722 kg ha^?1 year^?1. High runoff volumes occurred in July, August, and September, but April, June, the last 10 days of September and October, were the susceptible periods for soil erosion in the study area because of low plant cover and many agricultural activities during these periods.     

A grid-based rainfall-runoff model for flood simulation including paddy fields

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 (EQ_p), and the absolute error of peak runoff (ET_p) 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.     

Comparative effectiveness of different infiltration models in estimation of watershed flood hydrograph

The present study aims to evaluate performance of different infiltration models, namely initial and constant rate, soil conservation service (SCS) curve number and Green–Ampt in simulation of flood hydrographs for the small-sized Amameh Watershed, Iran. To achieve the study purpose, the infiltration rates were measured using rainfall simulator in work units acquired through overlaying topography, land use, drainage network and soil hydrologic group maps. All parameters of the study infiltration models were determined with the help of the Infilt. software package. The performances of the models in simulation of the observed output hydrographs from the entire watershed were ultimately evaluated for 28 rainfall–runoff events in the HEC-HMS environment. The different components of the observed and estimated hydrographs including time to peak, runoff volume, peak discharge, discharge values and peak time deviation were compared using relative error (RE), coefficient of determination (R²), peak-weighted root mean square error (PWRMSE) and Nash–Sutcliffe (NS) criteria. The general performance of estimations was also qualitatively assessed using scatter plot and distribution of study variables around standard lines of 1:1 slope. The results revealed that the SCS infiltration model with PWRMSE = 0.61 m³ s^?1 and NS = 0.53 performed better than initial and constant rate model with PWRMSE = 1.1 m³ s^?1 and NS = 0.54, and Green Ampt model with PWRMSE = 1.35 m³ s^?1 and NS = 0.29 in estimation of flood hydrograph for the Amameh Watershed.     

Sediment yield modelling of an agricultural watershed using MUSLE, remote sensing and GIS

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.     

Potential rainwater storage capacity of irrigation ponds

From antiquity to the present, Japan has irrigated many paddy fields from irrigation ponds. There are some 64,000 such irrigation ponds with a benefit area of over 2 ha each. These irrigation ponds not only function as a water-source for the stable production of food, but also are thought to reduce flooding in lower regions through temporary storage of rainwater and catchment runoff because they are located upstream of paddy fields, upland fields and residential land. Centering our research on Kagawa and Osaka Prefectures, we assessed the potential of rainwater storage capacity created by free space in irrigation ponds resulting from irrigation at a macro level as an indicator of flood mitigation. In these prefectures, potential rainwater storage capacity of irrigation ponds in early September was 2.1 and 1.4 times that of the potential storage capacity of associated paddy fields in an ordinary year.     

Prioritizing locations for the riparian establishment based on spatiotemporal change of riparian forest area at a watershed scale

A majority of streams in Korea have been channelized and their adjacent flood plains have been converted for anthropogenic land use, especially in urbanized areas. Fortunately, recent elevated public recognition to the stream ecosystem has led to governmental efforts to conserve riparian areas. In this study, a simple method to prioritize locations for riparian establishment was developed at a watershed scale based on spatiotemporal change of riparian forest area. The developed method was applied for the Ansung and Sapkyo watersheds, which were under consideration for the stream riparian area establishment by the Korean Ministry of Environment. Two riparian forest indices, Riparian Forest Index (RFI) and Riparian Forest Change Index (RFCI) were developed to represent spatial and temporal change of watershed riparian forest, respectively. LANSAT satellite images with a 30 m × 30 m resolution were used to estimate the two riparian forest indices. A precautionary approach, which intends to preserve the existing riparian forests as much as possible, was applied by ranking sub-watersheds based on the two riparian forest indices to prioritize locations for the riparian establishment at a sub-watershed level. The results showed that overall urban land cover in riparian areas increased while forests and cropland decreased over the past 25 years. More importantly, riparian forest removal occurred more rapidly in the riparian area, which is one of the most important niches for riparian ecosystems, as compared to the entire watershed. Most riparian forests appeared to be located upstream of the watersheds, and thus it is important to develop management measures to preserve existing riparian forests from human activities. The developed approach could be a useful tool that can assist policy makers to prioritize locations for the riparian area establishment. However, this method has limitations of only considering riparian forest area and therefore, other aspects such as stream morphology as well as ecology needs to be incorporated into riparian area determination process as they become available in the future. In addition, considering that substantial portions of riparian areas have already been disturbed, the restoration aspect of the impaired riparian also needs to be investigated further.     

Future potential impacts of climate change on agricultural watershed hydrology and the adaptation strategy of paddy rice irrigation reservoir by release control

This study is to assess the climate change impact on the temporal variation of paddy rice irrigation reservoir water level from the future evaluated watershed inflow, and to suggest an adaptation method of the future reservoir water level management for stable water supply of paddy irrigation demands. A 366.5 km² watershed including two irrigation reservoirs located in the upper middle part of South Korea was adopted. For the future evaluation, the SLURP model was set up using 9 years daily reservoir water level and streamflow records at the watershed outlet. The average Nash-Sutcliffe model efficiencies for calibration and validation were 0.69 and 0.65, respectively. For the future climate condition, the NIES MIROC3.2 hires data by SRES A1B and B1 scenarios of the IPCC was adopted. The future data were downscaled by applying Change Factor statistical method through bias-correction using 30 years past weather data. The results of future impact showed that the future reservoir storages of autumn and winter season after completion of irrigation period decreased for 2080s A1B scenario. Considering the future decrease of summer and autumn reservoir inflows, the reservoir operation has to be more conservative for preparing the water supply of paddy irrigation, and there should be a more prudent decision making for the reservoir release by storm events. Therefore, as the future adaptation strategy, the control of reservoir release by decreasing in August and September could secure the reservoir water level in autumn and winter season by reaching the water level to almost 100% like the present reservoir water level management.     

A combined technique of floodplain storage and reservoir irrigation for paddy rice cultivation

This paper introduces an irrigation system developed in the floodplain of a lake and studies the water management technique of the irrigation system by estimating the total water balance of the whole system. The system is characterized by a reservoir combined with a dike system in the floodplain of the Tonle Sap Great Lake and an irrigation system. Two main models are used for calculating the total water balance. The first model is the water balance of the reservoir. The inputs to the model are water level of the reservoir, precipitation, lake evaporation, infiltration, and area–volume curve of the reservoir. The outputs are inflow and outflow of the reservoir. The supply from the reservoir to paddy fields is computed from the outflow. The second model is the water balance of paddy fields, based on which the water requirement in paddy fields is derived. The reference evapotranspiration needed to calculate the water requirement is simulated for monthly time series using the FAO Penman–Monteith model. Since there is no drainage network in the irrigation system, surface drainage and runoff are not included in the calculation of the water balance, and seepage is considered negligible in the flat floodplain area. The evapotranspiration, rice variety, soil type and irrigated area are used to simulate water consumption in paddy fields. Finally, the two models are connected to produce the total water balance from the reservoir to paddy fields. The total outflow from the reservoir is estimated and the total water consumption for dry season cultivation is also determined. Finally, the efficiency of the whole system is examined.     

Assessing the effect of watershed slopes on recharge/baseflow and soil erosion

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.     

The pollutant loads from a paddy field watershed due to agricultural activity

Observations were performed in a small agricultural watershed for four consecutive irrigation periods in order to characterize fluctuations in the characteristics of pollutant runoff from paddy fields. During the puddling and rice-planting period and at the beginning of the mid-summer drainage period, both the pollutant concentrations and pollutant loadings of suspended solids, total nitrogen, and total phosphorus increased. In contrast, the pollutant net loading of total nitrogen was negative during the intermittent irrigation period. These results indicate that changes in the specific agricultural activities in the paddy fields cause temporal fluctuations of the pollutant runoff. Previous studies which focused on paddy fields have dealt with unit loading for entire irrigation period only. However, the unit loading for the entire irrigation period cannot take into account pollutant loading fluctuations due to differences in agricultural activity. Thus the unit loading of pollutant should be evaluated for each agricultural activity during the irrigation period.     

A comparative study on grid-based storm runoff prediction using Thiessen and spatially distributed rainfall

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.     

Evaluation of pollutant removal in a constructed irrigation pond

A year-long study on the water quality and hydrology was carried out to investigate the characteristics of the pollutant concentrations and pollutant removal in a constructed irrigation pond. The pond is part of a circular irrigation system for paddy fields within Lake Kasumigaura watershed, Japan. The average concentrations of the total nitrogen (TN), chemical oxygen demand (COD), total phosphorus (TP), and suspended solids (SS) at the pond outlet were 7.4, 8.6, 0.2, and 18.8 mg L⁻¹, respectively. The average removed loads for the same indices were 0.14, 2.47, 0.11, and 24.2 g m⁻² day⁻¹, respectively. The percentages of pollutant removals from the inflow loads for the same indices were 3, 26, 42, and 63%, respectively. The pond discharged the TN loads of 128 kg due to sediments stirred by operation of a pump for April and May. The average TN removal was 19% from June to August and was smaller than that reported in published literatures (40–50%). Major reasons were considered to be that the turnover of water in the pond was rapid (86% per day) and that the TN concentration of inflow water was relatively low (5.9 mg L⁻¹). The percentages of pollutants that flowed into the pond to the outflow loads from the study site were 6.6, 4.8, 1.6, and 1.1% for TN, COD, TP, and SS loads, respectively. The pollutant removal will be increased if the design of the circular irrigation system is reconsidered to utilize a pollutant removal function in the irrigation pond.     

A distributed hydro-environmental watershed model with three-zoned cell profiling

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.     

Simulation of water quality with the application of system dynamics model for population and land-use changes

Water quality is degraded due to urbanization because it causes population growth and land-use changes in a watershed. These changes are usually simulated using a linear equation; however, in reality, population and land use are very closely related. A watershed system dynamics model (WSD model) was developed in the simulation of the relation among population, land use (paddy fields, upland fields, forest, and household), and runoff. The model comprised of three sectors: the agricultural sector, nature sector, and urban sector. The elements in the WSD model were selected based on interviews with local government officers and references. The WSD model simulated population, land use, and runoff with an average relative error of about 5%. Total nitrogen (T-N) and total phosphorus (T-P) were simulated using the results of the WSD model and unit effluent loads. Field surveys were conducted to determine the rate of mitigation in paddy fields. In addition, correction equations for runoff and phosphate-containing detergent were introduced. The model simulated T-N with an average relative error of 9%, and T-P with 27%; a sensitivity analysis for the principal elements in the WSD model showed reasonable results.     

A physically based FVM watershed model fully coupling surface and subsurface water flows

A sophisticated modeling approach for simulating-coupled surface and subsurface flows in a watershed is presented. The watershed model developed is a spatially distributed physically based model of composite dimension, consisting of 3-D variably saturated groundwater flow submodel, 2-D overland flow submodel and 1-D river flow submodel. The 3-D subsurface flow is represented by the complete Richards equation, while the 2-D and 1-D surface flows by the diffusive approximations of their complete dynamic equations. For piecewise integration of these equations, the finite volume method (FVM) is employed assuming unknown variables such as the water depth and the pressure head to be volume-averaged state ones. Problem plane geometry is meshed with the unstructured cells of triangular shape which conforms to external as well as internal irregular boundaries such as those between 1-D and 2-D flows. A cell size controlling scheme, referred to as quasi-adaptive meshing scheme, is introduced to keep the local discretization errors caused by topographic elevation gradient even over the entire-meshed geometry. Performance of the model is tested through its practical application to a rugged intermountain watershed. Tuning the values of the three key parameters ensures successful calibration of the model. Once the model is so calibrated, it could reproduce satisfactory runoff response to any rainfall event. Expansion and shrinkage of the contributing area importantly affecting the direct runoff, caused by the vicissitude of rainfall during its total duration, are well reproduced, like what the commonly accepted runoff theory argues. It is thus concluded that the model developed could serve as a powerful watershed simulator usable for investigating and assessing the hydrological aspect of a watershed.     

Simulation of rainfall runoff and pollutant load for Chikugo River basin in Japan using a GIS-based distributed parameter model

In watershed management, the determination of peak and total runoff due to rainfall and prediction of pollutant load are very important. Measurement of rainfall runoff and pollutant load is always the best approach but is not always possible at the desired time and location. In practice, diffuse pollution has a complex natural dependence on various land-use activities such as agriculture, livestock breeding, and forestry. Estimation of pollutant load is therefore essential for watershed management and water pollution control. In this study, a model of rainfall runoff and pollutant load, which uses a geographical information system (GIS) database, is a convenient and powerful tool for resolving the abovementioned complexities. This technology was applied in order to simulate the runoff discharge and the pollutant load of total nitrogen (TN) and total phosphorus (TP) in the Chikugo River basin of Kyushu Island, Japan. First, a hydrologic modeling system (HEC-HMS) and GIS software extension tool were used for simulations of elevation, drainage line definition, watershed delineation, drainage feature characterization, and geometric network generation. The spatial distributions of land cover, soil classes, rainfall, and evaporation were then analyzed in order to simulate the daily runoff discharge at the Chikugo Barrage from April 2005 to December 2007. An important point in this approach is that a new development for data input processing with HEC-HMS was introduced for optimizing parameters of the model. Next, the water quality indicators TN and TP were examined, and an efficient approach was investigated for estimating monthly pollutant loads directly from unit load and ground-observed hydrological data. Both nonpoint and point sources of pollutants were considered, including different land-cover categories, sewers, factories, and livestock farms. The observed and simulated results for the runoff discharges and pollutant loads were in good agreement and totally consistent, indicating that the proposed model is applicable to simulation of rainfall runoff and pollutant load in the Chikugo River basin. Further, this model will be able to provide managers with a useful tool for optimizing the water surface management of this river basin.     

Surface and subsurface losses of N and P from salt-affected rice paddy fields of Saemangeum reclaimed land in South Korea

The present study was carried out to evaluate nutrient losses that occur during the course of agricultural activity from rice paddy fields of reclaimed tidal flat. For this study, we chose a salt-affected rice paddy field located in the Saemangeum reclaimed tidal area, which is located on the western South Korean coasts. The plot size was 1,000 m² (40 m × 25 m) with three replicates. The soil belonged to the Gwanghwal series, i.e., it was of the coarse silty, mixed, mesic type of Typic Haplaquents (saline alluvial soil). The input quantities of nitrogen and phosphorus (as chemical fertilizer) into the experimental rice paddy field were 200 kg N ha⁻¹ and 51 kg P₂O₅ ha⁻¹ per annum, and the respective input quantities of each due to precipitation were 9.3–12.9 kg N ha⁻¹ and 0.4–0.7 kg P ha⁻¹ per annum. In terms of irrigation water, these input quantities were 4.5–8.2 kg N ha⁻¹ and 0.3–0.9 kg P ha⁻¹ per annum, respectively. Losses of these nutrients due to surface runoff were 22.5–38.1 kg N ha⁻¹ and 0.7–2.2 kg P ha⁻¹ for the year 2003, and 26.8–29.6 kg N ha⁻¹ and 1.6–1.9 kg P ha⁻¹ for the year 2004, respectively. Losses of these nutrients due to subsurface infiltration during the irrigation period were 0.44–0.67 kg N ha⁻¹ and 0.03–0.04 kg P ha⁻¹ for the year 2003, and 0.15–0.16 kg N ha⁻¹ and 0.05–0.06 kg P ha⁻¹ for 2004. When losses of nitrogen and phosphorus were compared to the amount of nutrients supplied by chemical fertilizers, it was found that 11.3–19.1% of nitrogen and 0.5–1.7% of phosphorus were lost via surface runoff, whereas subsurface losses accounted to 0.2–0.8% for nitrogen and only 0.02–0.04% for phosphorus during the 2-year study period.     

Interval number fuzzy linear programming for climate change impact assessments of reservoir active storage

The major uncertainty in the climate change impact study inherits from applying the predictions of General Circulation Models (GCMs). Different results might be obtained by using various GCMs’ predictions, which causes difficulties on the decision making of water resources management. This study proposed an integrated hydrological simulations and optimization framework, consisting of a fuzzy linear programming model with interval numbers, a streamflow simulation model, and agricultural water demand projections, to evaluate the impacts of climate change on reservoir active storage. The reservoir inflows are simulated by the WatBal model, while agricultural water demands are predicted based on the projected change of potential evapotranspiration. Inflows and water demands are used to formulate an interval number fuzzy linear programming model. Fuzzy relationships are used to describe tolerable deficits of water resources, and the interval number is employed to indicate ranges of possible inflows and water demands. This systematic framework is applied to study the Tsengwen reservoir watershed to provide an optimal interval of active storage. The results further indicate the higher tolerable deficit, the smaller difference between superior and inferior active storage.     

Systematic assessment of flood mitigation in a tank irrigated paddy fields area

Flood mitigation in irrigation tanks and paddy fields is their favorable aspect though its practical effect is not known very well. A dynamic and systematic approach is presented to assess flood mitigation in a tank irrigated paddy fields area in the worst case where no static buffer function is expected. Based on the linear control theory, transfer function models for runoff process in catchments are identified. Hydraulic models are developed to represent flood dynamics in irrigation tanks, paddy fields, and drainage channels. These models are integrated as an ordinary differential equations system. Then, using the perturbed linear system, flood mitigation in each component of the system is examined in terms of frequency response. An application example demonstrates that a tank irrigated paddy fields area has a significant flood mitigation effect as a low-pass filter. This method has the advantage of assessing flood mitigation even in the case of an increase in the total runoff ratio.     

Modification of SWAT auto-calibration for accurate flow estimation at all flow regimes

To secure accuracy in the Soil and Water Assessment Tool (SWAT) simulation for various hydrology and water quality studies, calibration and validation should be performed. When calibrating and validating the SWAT model with measured data, the Nash–Sutcliffe efficiency (NSE) is widely used, and is also used as a goal function of auto-calibration in the current SWAT model (SWAT ver. 2009). However, the NSE value has been known to be influenced by high values within a given dataset, at the cost of the accuracy in estimated lower flow values. Furthermore, the NSE is unable to consider direct runoff and baseflow separately. In this study, the existing SWAT auto-calibration was modified with direct runoff separation and flow clustering calibration, and current and modified SWAT auto-calibration were applied to the Soyanggang-dam watershed in South Korea. As a result, the NSE values for total streamflow, high flow, and low flow groups in direct runoff, and baseflow estimated through modified SWAT auto-calibration were 0.84, 0.34, 0.09, and 0.90, respectively. The NSE values of current SWAT auto-calibration were 0.83, 0.47, ?0.14, and 0.90, respectively. As shown in this study, the modified SWAT auto-calibration shows better calibration results than current SWAT auto-calibration. With these capabilities, the SWAT-estimated flow matched the measured flow data well for the entire flow regime. The modified SWAT auto-calibration module developed in this study will provide a very efficient tool for the accurate simulation of hydrology, sediment transport, and water quality with no additional input datasets.