Hydrological Simulation Program-Fortran Research Articles

실측 하천 단면자료를 이용한 HSPF 유역모델의 수리정확도 개선

The hydrological simulation program FORTRAN (HSPF) is a comprehensive watershed model that employs the hydraulic function table (FTABLE) (depth-area-volume-flow relationship) to represent the geometric and hydraulic properties of water bodies. The hydraulic representation of the HSPF model mainly depends on the accuracy of the FTABLES. These hydraulic representations determine the response time of water quality state variables and also control the scour, deposition, and transport of sediments in the water body. In general, FTABLES are automatically generated based on reach information such as mean depth, mean width, length, and slope along with a set of standard assumptions about the geometry and hydraulics of the channel, so these FTABLES are unable to accurately describe the geometry and hydraulic behavior of rivers and reservoirs. In order to compensate the weakness of HSPF for hydraulic modeling, we generated alternate method to improve the accuracy of FTABLES for rivers, using the surveyed cross sections and rating curves. The alternative method is based on the hydraulics simulated by HEC-RAS using the surveyed cross sections and rating curves, and it could significantly improve the accuracy of FTABLES. Although the alternate FTABLE greatly improved the hydraulic accuracy of the HSPF model, it had little effect on the hydrological simulation.

Characterizing Changes in Streamflow and Sediment Supply in the Sacramento River Basin, California, Using Hydrological Simulation Program—FORTRAN (HSPF)

A daily watershed model of the Sacramento River Basin of northern California was developed to simulate streamflow and suspended sediment transport to the San Francisco Bay-Delta. To compensate for sparse data, a unique combination of model inputs was developed, including meteorological variables, potential evapotranspiration, and parameters defining hydraulic geometry. A slight decreasing trend of sediment loads and concentrations was statistically significant in the lowest 50% of flows, supporting the observed historical sediment decline. Historical changes in climate, including seasonality and decline of snowpack, contribute to changes in streamflow, and are a significant component describing the mechanisms responsible for the decline in sediment. Several wet and dry hypothetical climate change scenarios with temperature changes of 1.5 °C and 4.5 °C were applied to the base historical conditions to assess the model sensitivity of streamflow and sediment to changes in climate. Of the scenarios evaluated, sediment discharge for the Sacramento River Basin increased the most with increased storm magnitude and frequency and decreased the most with increases in air temperature, regardless of changes in precipitation. The model will be used to develop projections of potential hydrologic and sediment trends to the Bay-Delta in response to potential future climate scenarios, which will help assess the hydrological and ecological health of the Bay-Delta into the next century.

Modeling the influence of climate change on watershed systems: Adaptation through targeted practices

Climate change may influence hydrologic processes of watersheds (IPCC, 2013) and increased runoff may cause flooding, eroded stream banks, widening of stream channels, increased pollutant loading, and consequently impairment of aquatic life. The goal of this study was to quantify the potential impacts of climate change on watershed hydrologic processes and to evaluate scale and effectiveness of management practices for adaptation. We simulate baseline watershed conditions using the Hydrological Simulation Program Fortran (HSPF) simulation model to examine the possible effects of changing climate on watershed processes. We also simulate the effects of adaptation and mitigation through specific best management strategies for various climatic scenarios. With continuing low-flow conditions and vulnerability to climate change, the Ipswich watershed is the focus of this study. We quantify fluxes in runoff, evapotranspiration, infiltration, sediment load, and nutrient concentrations under baseline and climate change scenarios (near and far future). We model adaptation options for mitigating climate effects on watershed processes using bioretention/raingarden Best Management Practices (BMPs). It was observed that climate change has a significant impact on watershed runoff and carefully designed and maintained BMPs at subwatershed scale can be effective in mitigating some of the problems related to stormwater runoff. Policy options include implementation of BMPs through education and incentives for scale-dependent and site specific bioretention units/raingardens to increase the resilience of the watershed system to current and future climate change.

Entropy based groundwater monitoring network design considering spatial distribution of annual recharge

This study explores the inclusion of a groundwater recharge based design objective and the impact it has on the design of optimum groundwater monitoring networks. The study was conducted in the Hamilton, Halton, and Credit Valley regions of Ontario, Canada, in which the existing Ontario Provincial Groundwater Monitoring Network was augmented with additional monitoring wells. The Dual Entropy-Multiobjective Optimization (DEMO) model was used in these analyses. The value of using this design objective is rooted in the information contained within the estimated recharge. Recharge requires knowledge of climate, geomorphology, and geology of the area, thus using this objective function can help account for these physical characteristics. Two sources of groundwater recharge data were examined and compared, the first was calculated using the Precipitation-Runoff Modeling System (PRMS), and the second was an aggregation of recharge found using both the PRMS and Hydrological Simulation Program-Fortran (HSP-F). The entropy functions are used to identify optimal trade-offs between the maximum information content and the minimum shared information between the monitoring wells. The recharge objective will help to quantify hydrological characteristics of the vadose zone, and thus provide more information to the optimization algorithm. Results show that by including recharge as a design objective, the spatial coverage of the monitoring network can be improved. The study also highlights the flexibility of DEMO and its ability to incorporate additional design objectives such as the groundwater recharge.

A comparison of results from a hydrologic transport model (HSPF) with distributions of sulfate and mercury in a mine-impacted watershed in northeastern Minnesota

The St. Louis River watershed in northeast Minnesota hosts a major iron mining district that has operated continuously since the 1890s. Concern exists that chemical reduction of sulfate that is released from mines enhances the methylation of mercury in the watershed, leading to increased mercury concentrations in St. Louis River fish. This study tests this idea by simulating the behavior of chemical tracers using a hydrologic flow model (Hydrologic Simulation Program FORTRAN; HSPF) and comparing the results with measured chemistry from several key sites located both upstream and downstream from the mining region. It was found that peaks in measured methylmercury (MeHg), total mercury (THg), dissolved organic carbon (DOC), and dissolved iron (Fe) concentrations correspond to periods in time when modeled recharge was dominated by active groundwater throughout the watershed. This helps explain why the timing and size of the MeHg peaks was nearly the same at sites located just upstream and downstream from the mining region. Both the modeled percentages of mine water and the measured sulfate concentrations were low and computed transit times were short for sites downstream from the mining region at times when measured MeHg reached its peak. Taken together, the data and flow model imply that MeHg is released into groundwater that recharges the river through riparian sediments following periods of elevated summer rainfall. The measured sulfate concentrations at the upstream site reached minimum concentrations of approximately 1 mg/L just as MeHg reached its peak, suggesting that reduction of sulfate from non-point sources exerts an important influence on MeHg concentrations at this site. While mines are the dominant source of sulfate to sites downstream from them, it appears that the background sulfate which is present at only 1–6 mg/L, has the largest influence on MeHg concentrations. This is because point sourced sulfate is transported generally under oxidized conditions and is not flushed through riparian sediments in a gaining stream watershed system.

Methodology and Application of the Combined SWAT-HSPF Model

This paper shows the output of a research study that involves developing a new model for diffuse source pollution requiring the integration of a complex distributed catchment model with a model of contaminant transport. It explains in details the various model components, modifications and assumptions that have been made in the construction of the new combined model (NCM) based on Hydrological modules of Hydrological Simulation Program FORTRAN (HSPF) and Phosphorus transformations modules of Soil and Water Assessment Tool (SWAT) model, as well as the approach adopted. Three Irish catchments have been tested, namely Oona, Bawn and Dripsey. Model performance for both calibration and validation periods, and model parameter sensitivity and uncertainty analysis results were examined extensively with the outputs of SWAT model and HSPF. The NCM showed promising potential for better estimation of phosphorus losses from catchments for Irish conditions with some drawback for baseflow dominant catchments. It gives good results in terms of flow and phosphorus modelling, and is generally better than SWAT or HSPF alone for most of the cases tested. An uncertainty analysis based on model parameters was conducted using the PARASOL method implemented in SWAT 2005, and uncertainty bounds for the flow and the total P load predictions were compared with the observed values for each catchment.

Hydrologic Evaluation of River Basin Scale Tillage Effects on Non‐Point Source Loads from Upland Crop Areas†

AbstractThis study used the Hydrological Simulation Program—Fortran (HSPF) model to evaluate the river basin scale effects of nonpoint source (NPS) pollution loads caused by tillage and no‐tillage applications to upland crop areas. The study site was the Byulmi‐cheon river basin (1.21 km2) of South Korea. Hourly rainfall, discharge and stream water quality data for 2 years (2012–2013) were collected at the river basin outlet. The HSPF model under tillage conditions was calibrated using 23 rainfall events with an average Nash–Sutcliffe model efficiency value for runoff of 0.61 and determination coefficients for sediment, total nitrogen (T‐N) and total phosphorus (T–P) of 0.58, 0.61 and 0.62 respectively. The field experiment results from the no‐tillage plots with slopes of 3 and 8% under radish and sesame cultivation showed decreases in the runoff ratio, sediment, T‐N and T–P of 10.8, 81.7, 11.9 and 17.1% respectively. The HSPF model parameters soil bulk density (BD) and soil infiltration capacity (INFILT) were controlled for the upland crop areas during the evaluation of the no‐tillage effects. By increasing the parameter values from 1.33 Mg m−3 BD and 4.1 mm h−1 INFILT for the tillage condition to 1.90 Mg m−3 BD and 8.9 mm h−1 INFILT for the no‐tillage condition, the river basin runoff ratio and sediment, T‐N and T–P values were reduced by 10.3, 56.7, 18.3 and 35.9% respectively. Copyright © 2016 John Wiley & Sons, Ltd.

개발예정 도시의 수질교환법 적용을 위한 정책결정 시스템 제시

미국의 수질교환법의 제정 이후 이 법안의 적용을 위하여 많은 파일럿 프로그램과 프로젝트가 생성되었으나 실제로 수질교환이 이루어 지는 경우는 흔치 않은 현실이다. 수질교환법의 적용이 용이하지 않은 이유로 가장 큰 것은 교환 지역 양측간의 공정성을 확보하기가 쉽지 않기 때문이다. 또한 도시개발로 유발되는 비점오염원의 유출량으로 인한 하천의 환경영향의 불확실성이 정책입안자의 법안 적용을 더욱 어렵게 하고 있다. 본 논문은 수질 모델링 프로그램 중 도시의 불투수면의 유출을 모의하기에 유용한 Hydrological Simulation Program-Fortran (HSPF)을 이용하여 미래의 도시개발 시나리오에 대응하는 점오염과 비점오염원 유출량을 도출하였다. 도시개발의 정도와 강우강도에 따른 부유탁도의 증가분을 계산 함으로써 향후 도시개발이 미치는 수질 영향을 하천 상 하류 간의 수질교환 단위로 전환하여 제시하였다. 제시된 지역 특화된 수질교환단위는 정책입안자와 이해관계자들에게 수질교환법 적용을 위한 정책결정 시스템으로 사용될 수 있다. There are many pilot programs and projects to implement the water quality trading (WQT) policy. But actual trading is relatively rare. The main reason of the scarce applications of WQT policy is the difficulty in determining the equalities between the trading sites. The uncertainty of the impacts of the nonpoint sources pollutant discharges between up and downstream urban development areas also makes the implementation of the policy harder. The simulated results from the watershed modeling program will be used to calculate the point and nonpoint sources pollutants of the future urban development scenarios. The amount of suspended sediments resulting from the urban developments and rainfall intensities will be used to indicate the environmental impacts of the water body between upstream and downstream. The water quality impacts after development scenarios to the outlet of the watershed were transferred to the trading units between two sites. The recommended trading units can be used as a decision support system for policy makers and stakeholders to carry out better WQT practices.

The Effect of Rice Straw Mulching and No-Tillage Practice in Upland Crop Areas on Nonpoint-Source Pollution Loads Based on HSPF

This study evaluates the watershed-scale effects of non-point-source (NPS) pollution loads caused by rice straw mulching and no-tillage applications in upland crop areas using the Hydrological Simulation Program–Fortran (HSPF) model. The study area is the Byulmi-cheon watershed (1.21 km²) of South Korea. Hourly rainfall, discharge and stream water quality data were collected for three years (2011–2013) at the watershed outlet. The HSPF model under conventional (no rice straw mulching or tillage) conditions was calibrated and validated using 20 rainfall events for runoff and 14 rainfall events for stream water quality (sediment, T-N and T-P). The average Nash–Sutcliffe model efficiency value for runoff was 0.61, and determination coefficients for runoff, sediment, total nitrogen (T-N) and total phosphorus (T-P) were 0.70, 0.56, 0.58 and 0.61, respectively. The results of field experiments with slopes of 3% and 8% for radish and sesame cultivation showed decreases in the runoff ratio, sediment, T-N and T-P of 9.0%, 95.9%, 32.6% and 43.5% for rice straw mulching plots and 22.5%, 82.5%, 67.8 and 70.6% for no-tillage plots. The HSPF model parameters soil infiltration capacity (INFILT), soil bulk density (BD), wilting point (WP) and field capacity (FC) were controlled for the upland crop areas during the evaluation of the rice straw mulching and no-tillage effects. The HSPF evaluation using the application of Best Management Practices (BMPs) showed that the watershed runoff ratio, sediment, T-N and T-P values were reduced by 10.4%, 68.7%, 31.6% and 41.3% using rice straw mulching and 21.5%, 83.4%, 51.9% and 60.2% under no-tillage conditions compared with conventional conditions. The land use change scenarios for the baseline (upland crop areas 5%), Scenario 1 (upland crop areas 10%) and Scenario 2 (upland crop areas 30%) were applied in the model. The results of the evaluation show that the proportion of NPS pollution loads increased by a ratio approximately equal to that of the increasing upland crop area.

Urban Stormwater Management Model and Tools for Designing Stormwater Management of Green Infrastructure Practices

Urbanization is growing rapidly in Malaysia. Rapid urbanization has known to have several negative impacts towards hydrological cycle due to decreasing of pervious area and deterioration of water quality in stormwater runoff. One of the negative impacts of urbanization is the congestion of the stormwater drainage system and this situation leading to flash flood problem and water quality degradation. There are many urban stormwater management softwares available in the market such as Storm Water Drainage System design and analysis program (DRAINS), Urban Drainage and Sewer Model (MOUSE), InfoWorks River Simulation (InfoWork RS), Hydrological Simulation Program-Fortran (HSPF), Distributed Routing Rainfall-Runoff Model (DR3M), Storm Water Management Model (SWMM), XP Storm Water Management Model (XPSWMM), MIKE-SWMM, Quality-Quantity Simulators (QQS), Storage, Treatment, Overflow, Runoff Model (STORM), and Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS). In this paper, we are going to discuss briefly about several softwares and their functionality, accessibility, characteristics and components in the quantity analysis of the hydrological design software and compare it with MSMA Design Aid and Database. Green Infrastructure (GI) is one of the main topics that has widely been discussed all over the world. Every development in the urban area is related to GI. GI can be defined as green area build in the develop area such as forest, park, wetland or floodway. The role of GI is to improve life standard such as water filtration or flood control. Among the twenty models that have been compared to MSMA SME, ten models were selected to conduct a comprehensive review for this study. These are known to be widely accepted by water resource researchers. These ten tools are further classified into three major categories as models that address the stormwater management ability of GI in terms of quantity and quality, models that have the capability of conducting the economic analysis of GI and models that can address both stormwater management and economic aspects together.

A comparison of ANN and HSPF models for runoff simulation in Gharehsoo River watershed, Iran

In this study, the capability of two different types of model including Hydrological Simulation Program-Fortran (HSPF) as a process-based model and Artificial Neural Networks (ANNs) as a data-driven model in simulating runoff were evaluated. The area considered is the Gharehsoo River watershed in northwest Iran. HSPF is a semi distributed Deterministic, continuous and physically-Based model that can simulate the hydrologic, associated water quality and quantity, processes on pervious and impervious land surfaces and streams. ANN is probably the most successful machine learning technique with flexible mathematical structure which is capable of identifying complex non-linear relationships between input and output data without attempting to reach understanding as to the nature of the phenomena. Statistical approach depending on cross-, auto- and partial-autocorrelation of the observed data is used as a good alternative to the trial and error method in identifying model inputs. The performance of ANN and HSPF models in calibration and testing stages are compared with the observed runoff values to identify the best fit forecasting model based upon a number of selected performance criteria. Results of runoff simulation indicate that simulated runoff by ANN were generally closer to observed values than those predicted by HSPF.

Spatially-Distributed Cost-Effectiveness Analysis Framework to Control Phosphorus from Agricultural Diffuse Pollution.

Best management practices (BMPs) for agricultural diffuse pollution control are implemented at the field or small-watershed scale. However, the benefits of BMP implementation on receiving water quality at multiple spatial is an ongoing challenge. In this paper, we introduce an integrated approach that combines risk assessment (i.e., Phosphorus (P) index), model simulation techniques (Hydrological Simulation Program–FORTRAN), and a BMP placement tool at various scales to identify the optimal location for implementing multiple BMPs and estimate BMP effectiveness after implementation. A statistically significant decrease in nutrient discharge from watersheds is proposed to evaluate the effectiveness of BMPs, strategically targeted within watersheds. Specifically, we estimate two types of cost-effectiveness curves (total pollution reduction and proportion of watersheds improved) for four allocation approaches. Selection of a ‘‘best approach” depends on the relative importance of the two types of effectiveness, which involves a value judgment based on the random/aggregated degree of BMP distribution among and within sub-watersheds. A statistical optimization framework is developed and evaluated in Chaohe River Watershed located in the northern mountain area of Beijing. Results show that BMP implementation significantly (p >0.001) decrease P loss from the watershed. Remedial strategies where BMPs were targeted to areas of high risk of P loss, deceased P loads compared with strategies where BMPs were randomly located across watersheds. Sensitivity analysis indicated that aggregated BMP placement in particular watershed is the most cost-effective scenario to decrease P loss. The optimization approach outlined in this paper is a spatially hierarchical method for targeting nonpoint source controls across a range of scales from field to farm, to watersheds, to regions. Further, model estimates showed targeting at multiple scales is necessary to optimize program efficiency. The integrated model approach described that selects and places BMPs at varying levels of implementation, provides a new theoretical basis and technical guidance for diffuse pollution management in agricultural watersheds.

The effect of DEM and land use spatial resolution on simulated streamflow and sediment

<div> <p>The Hydrologic Simulation Program-FORTRAN (HSPF) model is widely used to develop management strategies for water resources and to evaluate the hydrologic effect of various management scenarios. The spatial resolution of the input data used to parameterize HSPF model may induce uncertainty in model outputs. In this study, the impact of spatial resolutions of Digital Elevation Model (DEM) and land use map on the uncertainty of HSPF predicted flow and sediment were evaluated. DEM resolution can affect stream length, watershed area and average slope, whereas land use data resolution can lead to redistribution of land use information. Results showed that finer resolution DEM and land use maps can generate higher flow volumes and sediment loads compared to modelling scenarios using inputs of coarse resolution. The relative change in model performance between the baseline scenario (high-resolution) and scenarios of coarser resolution described uncertainties due to DEM and land use spatial information, and the probability density function of these uncertainties was used to estimate these uncertainties. Modelled flow and sediment uncertainty due to DEM resolution seems to follow a log-normal and a general extreme value distribution respectively, whereas modelled flow and sediment uncertainty due to land use resolution seems to both follow a general extreme value distribution. Overall, results highlight the need for a high-resolution DEM and land use maps in the application of the HSPF model while they provide useful information for reducing the model uncertainties.</p> </div> <p> </p>

Watershed model calibration framework developed using an influence coefficient algorithm and a genetic algorithm and analysis of pollutant discharge characteristics and load reduction in a TMDL planning area

Manual calibration is common in rainfall-runoff model applications. However, rainfall-runoff models include several complicated parameters; thus, significant time and effort are required to manually calibrate the parameters individually and repeatedly. Automatic calibration has relative merit regarding time efficiency and objectivity but shortcomings regarding understanding indigenous processes in the basin. In this study, a watershed model calibration framework was developed using an influence coefficient algorithm and genetic algorithm (WMCIG) to automatically calibrate the distributed models. The optimization problem used to minimize the sum of squares of the normalized residuals of the observed and predicted values was solved using a genetic algorithm (GA). The final model parameters were determined from the iteration with the smallest sum of squares of the normalized residuals of all iterations. The WMCIG was applied to a Gomakwoncheon watershed located in an area that presents a total maximum daily load (TMDL) in Korea. The proportion of urbanized area in this watershed is low, and the diffuse pollution loads of nutrients such as phosphorus are greater than the point-source pollution loads because of the concentration of rainfall that occurs during the summer. The pollution discharges from the watershed were estimated for each land-use type, and the seasonal variations of the pollution loads were analyzed. Consecutive flow measurement gauges have not been installed in this area, and it is difficult to survey the flow and water quality in this area during the frequent heavy rainfall that occurs during the wet season. The Hydrological Simulation Program-Fortran (HSPF) model was used to calculate the runoff flow and water quality in this basin. Using the water quality results, a load duration curve was constructed for the basin, the exceedance frequency of the water quality standard was calculated for each hydrologic condition class, and the percent reduction required to achieve the water quality standard was estimated. The R2 value for the calibrated BOD5 was 0.60, which is a moderate result, and the R2 value for the TP was 0.86, which is a good result. The percent differences obtained for the calibrated BOD5 and TP were very good; therefore, the calibration results using WMCIG were satisfactory. From the load duration curve analysis, the WQS exceedance frequencies of the BOD5 under dry conditions and low-flow conditions were 75.7% and 65%, respectively, and the exceedance frequencies under moist and mid-range conditions were higher than under other conditions. The exceedance frequencies of the TP for the high-flow, moist and mid-range conditions were high and the exceedance rate for the high-flow condition was particularly high. Most of the data from the high-flow conditions exceeded the WQSs. Thus, nonpoint-source pollutants from storm-water runoff substantially affected the TP concentration in the Gomakwoncheon.

Assessing a fuzzy model and HSPF to supplement rainfall data for nonpoint source water quality in the Feitsui reservoir watershed

The objective of this study was to improve the use of a fuzzy model to supplement rainfall data when the watershed's meteorological station is either far away or suffers a loss of rainfall data. The fuzzy model can also supplement rainfall data when the station is nearby. The accuracy of rainfall data in the EPA's (Environmental Protection Agency) BASINS (Better Assessment Science Integrating Point and Nonpoint Sources) decision support tool is affected by the sparse meteorological data contained in BASINS. This study also assessed the improvement in stream flow prediction with the Hydrological Simulation Program-FORTRAN (HSPF) model contained within BASINS, using the hourly precipitation estimates for the Feitsui reservoir watershed. This study demonstrates that using a fuzzy model to supplement rainfall data has the potential to improve stream flow predictions, thus aiding water quality assessment in the nonpoint water quality assessment decision tool.

A Multi-Criteria Model Selection Protocol for Practical Applications to Nutrient Transport at the Catchment Scale

Process-based models are widely used to investigate nutrient dynamics for water management purposes. Simulating nutrient transport and transformation processes from agricultural land into water bodies at the catchment scale are particularly relevant and challenging tasks for water authorities. However, few practical methods guide inexperienced modelers in the selection process of an appropriate model. In particular, data availability is a key aspect in a model selection protocol, since a large number of models contain the functionalities to predict nutrient fate and transport, yet a smaller number is applicable to specific datasets. In our work, we aim at providing a model selection protocol fit for practical application with particular emphasis on data availability, cost-benefit analysis and user’s objectives. We select for illustrative purposes five process-based models with different complexity as “candidates” models: SWAT (Soil and Water Assessment Tool), SWIM (Soil and Water Integrated Model), GWLF (Generalized Watershed Loading Function), AnnAGNPS (Annualized Agricultural Non-Point Source Pollution model) and HSPF (Hydrological simulation program-FORTRAN). The models are described in terms of hydrological and chemical output and input requirements. The model selection protocol considers data availability, model characteristics and user’s objectives and it is applied to hypothetical scenarios. This selection method is particularly formulated to choose process-based models for nutrient modeling, but it can be generalized for other applications which are characterized by a similar degree of complexity.

Review of simulation research in hydrology and water quality based on HSPF model

Hydrological Simulation Program-Fortran(HSPF)is a comprehensively semi-distributed hydrological model and can simulate hydrological conditions and water quality accurately in watersheds.It has been extensively applied in the fields of water resources and environment.The article reviewed the model mechanism of hydrology,sediment erosion and migration of pollutants,and summarized the latest devolepments in the modeling of the runoff,the migration of pollutants,the influence of land use or land cover change and climate change on watersheds.Besides,the research directions of complete the model were discussed,including the migration mechanism of pollutant,the uncertainty of model parameters and the combination with other models.

Water and nonpoint source pollution estimation in the watershed with limited data availability based on hydrological simulation and regression model.

Nonpoint source (NPS) pollution is considered as the main reason for water quality deterioration; thus, to quantify the NPS loads reliably is the key to implement watershed management practices. In this study, water quality and NPS loads from a watershed with limited data availability were studied in a mountainous area in China. Instantaneous water discharge was measured through the velocity-area method, and samples were taken for water quality analysis in both flood and nonflood days in 2010. The streamflow simulated by Hydrological Simulation Program-Fortran (HSPF) from 1995 to 2013 and a regression model were used to estimate total annual loads of various water quality parameters. The concentrations of total phosphorus (TP) and total nitrogen (TN) were much higher during the flood seasons, but the concentrations of ammonia nitrogen (NH3-N) and nitrate nitrogen (NO3-N) were lower during the flood seasons. Nevertheless, only TP concentration was positively correlated with the flow rate. The fluctuation of annual load from this watershed was significant. Statistical results indicated the significant contribution of pollutant fluxes during flood seasons to annual fluxes. The loads of TP, TN, NH3-N, and NO3-N in the flood seasons were accounted for 58-85, 60-82, 63-88, 64-81% of the total annual loads, respectively. This study presented a new method for estimation of the water and NPS loads in the watershed with limited data availability, which simplified data collection to watershed model and overcame the scale problem of field experiment method.

Impacts of rainfall and air temperature variations due to climate change upon hydrological characteristics: a case study

Rainfall and air temperature variations resulting from climate change are important driving forces to change hydrologic processes in watershed ecosystems. This study investigated the impacts of past and future rainfall and air temperature variations upon water discharge, water outflow (from the watershed outlet), and evaporative loss in the Lower Yazoo River Watershed (LYRW), Mississippi, USA using the Hydrological Simulation Program-Fortran (HSPF) model. Four future climate change (i.e., rainfall and air temperature change) scenarios, namely the CSIROMK35A1B, HADCM3B2, CSIROMK2B2, and MIROC32A1B scenarios, were used as input data to perform simulations in this study. Results showed that monthly variations of water discharge, evaporative loss, and water outflow were primarily due to the monthly fluctuations of rainfall rather than air temperature. On average, for all of the four scenarios, a 6.4% decrease in rainfall amount resulted in, respectively, 11.8 and 10.3% decreases in water outflow and evaporative loss. Our study demonstrated that rainfall had profound impacts upon water outflow and evaporative loss. In light of this predicted future decrease in water outflow, water resource conservation practices such as reducing ground and surface water usages that help to prevent streams from drying are vitally important in mitigating climate change impacts on stream flow in the LYRW.

Estimating E. coli and Enterococcus loads in a coastal Texas watershed

Pathogens are the principal cause of water body impairment for 303(d) listed waters in Texas and across the United States with 10,654 impairments nationally (TCEQ 2012; USEPA 2013). In Texas, 45% of 568 total impairments are caused by elevated bacteria levels (TCEQ 2012). Models such as the Soil and Water Assessment Tool (SWAT) and Hydrological Simulation Program-FORTRAN (HSPF) have been used for assessing bacterial sources and loading. Other simplistic microbial models, such as the Potential Nonpoint Pollution Index (PNPI), Spatially Explicit Delivery MODel (SEDMOD), and Spatially Explicit Load Enrichment Calculation Tool (SELECT), have been developed to rank potential pollution impacts from nonpoint sources and identify critical areas primarily using land use and geomorphology. Citation: Borel K, Karthikeyan R, Berthold TA, Wagner K. 2014. Estimating E. coli and Enterococcus loads in a coastal Texas watershed. Texas Water Journal. 6(1):33-44. Available from: https://doi.org/10.21423/twj.v6i1.7008.