Vladimir J. Alarcon

IMPACTS OF LAND USE CHARACTERIZATION IN MODELING HYDROLOGY AND SEDIMENTS FOR THE LUXAPALLILA CREEK WATERSHED, ALABAMA AND MISSISSIPPI

The Hydrological Simulation Program - Fortran (HSPF), interfaced with the Better Assessment Science Integrating Point and Nonpoint (BASINS), was used to evaluate the impact of land use (as characterized by different land use/land cover (LU/LC) datasets) on hydrology and sediment components of the Luxapallila Creek watershed. The 1,770 km2 watershed is located in Alabama and Mississippi. Simulation of the watershed processes were tested at the hillslope and at the watershed outlet for the period between 1985 and 2003. Three LU/LC databases were used: the Geographic Information Retrieval and Analysis System (GIRAS), the Moderate Resolution Imaging Spectroradiometer land cover product (MODIS MOD12Q1), and the National Land Cover Dataset (NLCD). The two main land use categories revealed by the three LU/LC databases were forest and agricultural lands. Whereas forest cover mechanisms were the main source of water loss in hydrology simulation, agricultural land was the main source of sediment export in sediment modeling. Land use datasets of coarser spatial resolution (MODIS and GIRAS) produced larger HSPF estimations for sediment fraction values than land use datasets identifying smaller percentages of those agricultural land cover classes (NLCD). Differences in agricultural land characterization among the land use datasets showed that sediment predictions were more sensitive than streamflow predictions to the scale and resolution of land use datasets. Choosing the right land use dataset will impact the modeling of sediments and, potentially, other water quality constituents that are related with agricultural activities.

A web-based simulation system for transport and retention of dissolved contaminants in soil

Abstract The movement of contaminants through the soil matrix is primarily a liquid phase process in which the chemical partitions between sorbed and dissolved phases. These phenomena have been modeled extensively and several computer models were developed. The use of those computer programs requires installation of the software in the users machine. Usually, post-processing of the numerical output provided by the software is required. In this paper, a web-based simulation environment for retention and transport of dissolved organic and inorganic compounds in soils is presented. The system was developed using Java and is based on the Multi-reaction Transport Model of heavy metals in soil. The mathematical and numerical formulation of the model is briefly sketched. The core computing components of the simulation environment were written in C or fortran for their computational efficiency. The emerging Java Native Interface (JNI) technique and the Swing interface were used to design a user-friendly simulator. Java security problems (due to the use of applets calling native libraries) are discussed and a solution to avoid security restrictions is provided. The simulation system provides interactive user control and real time visualization through standard web browsers. The Java-based simulation code was used to analyze a hypothetical soil contamination problem. The almost instantaneous visualization of results provided by the Java-based interface resulted in efficient and easy analyses. Although a performance comparison was not in mind, the evaluation of the same scenario using the original fortran code took three times as much total time (program run, evaluation of results and post-processing) as that using the Java simulation system.

A Hydrological Model of the Mobile River Watershed, Southeastern USA

A hydrological model of the Mobile Bay watershed located in the northern Gulf of Mexico, (Alabama, USA) is presented. The modeling of hydrological processes is performed using the Hydrological Simulation Program Fortran (HSPF). The project region was divided into two sectors for simplifying the modeling task: an upland watershed (that included streams not draining directly to the Mobile Estuary), and several watersheds of selected streams that drain directly to the Mobile estuary (namely: Fish River, Magnolia River, and Chickasaw Creek). The Better Assessment Science Integrating Point & Nonpoint Sources (BASINS) GIS system was used to perform most of the geospatial operations, although ArcGis and ArcInfo were also used to complement geospatial processing that was not available in BASINS.

Estimation and Propagation of Parameter Uncertainty in Lumped Hydrological Models: A Case Study of HSPF Model Applied to Luxapallila Creek Watershed in Southeast USA

Estimation and Propagation of Parameter Uncertainty in Lumped Hydrological Models: A Case Study of HSPF Model Applied to Luxapallila Creek Watershed in Southeast USA Explicit quantification of the uncertainty associated to the predictions of a hydrologic model is a necessary activity to objectively evaluate and report the limitations of the model caused by different sources of error. The current state of the practice of hydrologic modeling indicates that parametric uncertainty is considered as one of the most important sources of uncertainty. Some of the most relevant problems remaining in the practice include the identification of the principal parameters affecting model predictions and quantification of parameter ranges. This study evaluated stochastically one of the most popular deterministic watershed water quality models for decision making in USA.

Scale-Dependency and sensitivity of hydrological estimations to land use and topography for a coastal watershed in mississippi

This paper investigates the effect of land use and digital elevation models spatial resolution and scale on the simulation of stream flow in two coastal watersheds located in the Mississippi Gulf Coast (USA). Four elevation datasets were used: USGS DEM, NED, NASAs SRTM and IFSAR (300, 30, 30, and 5 meter resolution, respectively). Three land use datasets were included in this study: USGS GIRAS, NLCD, and NASA MODIS MOD12Q1 (400, 30, and 1000 m resolution, correspondingly). The Hydrological Program Fortran (HSPF) was used for estimating stream flow in the two watersheds. Results showed that swapping datasets in a factorial design experiment produce equivalent statistical fit of measured and simulated stream flow data. The results also showed that HSPF-estimated stream flows are not sensitive to scale and spatial resolution of the datasets included in the study.

Using hydrodynamic modeling for estimating flooding and water depths in grand bay, alabama

This paper presents a methodology for using hydrodynamic modeling to estimate inundation areas and water depths during a hurricane event. The Environmental Fluid Dynamic Code (EFDC) is used in this research. EFDC is one of the most commonly applied models to Gulf of Mexico estuaries. The event with which the hydrodynamic model was tested was hurricane Ivan. This hurricane made landfall at the Alabama Gulf Coast in September 16, 2004. Hurricane Ivan was the most severe hurricane to hit eastern Alabama. Results show that the EFDC model is able to generate instances of flooded areas before, during and after a hurricane event (Ivan hurricane). The model also estimated water depths and water surface elevation values consistent to measured data reported in the literature, and comparable to model-estimated data from a meso-scale Slosh model for the region (also reported in the literature).

Comparison of two hydrodynamic models of weeks bay, alabama

This paper presents a comparison of two hydrodynamic models of the Weeks Bay sub-estuary (Alabama, USA). One model was developed using the Environmental Fluid Dynamic Code (EFDC). The resulting model was compared to an existing hydrodynamic model (of the same water body) that was developed using the Adaptive Hydraulic modeling system (ADH). Comparisons were performed in terms of predicted water surface elevations in Weeks Bay. The computational grid was created using GEFDC (a mesh generator for EFDC) and NOAAs coastline and bathymetric data. The results showed that the EFDC model provides comparable water surface elevation (WSE) estimations for five out of seven control points located in the Weeks Bay study area. R2 values for those points range between 0.88 and 0.99. Root mean square error values are shown to be lower than 0.15 m in those cases. For the rest of the control points, R2 values range from 0.73 to 0.87 (RMSE range: 0.2 - 0.35), showing that the EFDC model provides acceptable estimations of WSE when compared to the ADH model WSE output. A finer computational mesh may improve EFDC WSE estimations for Weeks Bay as reported in the literature.

Simulation of Hydrograph Response to Land Use Scenarios for a Southern Chile Watershed

In this research, the hydrological response to changes in land use for the Quilmo River watershed (Southern Chile) is assessed. The assessment is performed using the Hydrological Simulation Program-Fortran code (HSPF). The hydrological response to predominant land uses of non-native planted forests, agricultural lands, grasslands, and native forests was sequentially simulated. The hydrological model was initially calibrated for stream flow at the exit of the watershed (R2 = 0.66, P < 0.001). The calibrated model was used for simulating the hydrological responses under two flood events: a peak flood (August 24, 2002), and a moderate flood of (October 14, 2002). The simulated land use scenarios were sequentially and independently input to the model. Results showed that for both flood-events the hydrological response to non-native forests or agricultural lands was very similar to the baseline hydrograph corresponding to 2002 land use. The hydrological response to predominant grasslands and native forests was significantly different. For the August 24 flood, the model calculates that extreme minimum flows and low base flows take place when native forest is the predominant land use. When the watershed is covered by grasslands the most balanced hydrograph (moderate droughts and moderate peak flows) is produced. For the moderate flood event of October 14, the highest values of peak flows and base flows were produced when the watershed is predominantly covered by grasslands. However, the hydrograph for grasslands still showed the most balanced response (moderate droughts and moderate peak flows). For native forests, the response hydrograph shows low base flows but also low peak flows. Therefore, combining grasslands with native forests may provide a balanced hydrograph not only with respect to magnitudes of flow (high base flows and moderated peak flows) but also on their timing. Both conditions are favorable for flood control and drought mitigation.

Assimilation of TRMM Precipitation into a Hydrological Model of a Southern Andes Watershed

This paper presents results of assimilation of TRMM precipitation into a hydrological model of Los Almendros River watershed, assessed by the comparison of simulated stream flow values to observed stream flow data. Los Almendros River is a tributary to the Clarillo River, located in Reserva Nacional Rio Clarillo (National Reserve Clarillo River), Chile, South America. Los Almendros basin, covering approximately 4.9 km2, is a typical Andean watershed with an average slope of 46.3. It drains an average of 18.5 L/s from a catchment area covered predominantly by grasslands (91%), while forests and savanna land cover types are less predominant (3% and 6% respectively). The hydrological model of Los Almendros watershed was developed using the Hydrological Simulation Program Fortran (HSPF). Results showed that raw TRMM precipitation time-series overestimated disaggregated precipitation values for the whole period of analysis. TRMM data required time-averaging for the monthly and annual values to be in the same range as those of disaggregated data. Time-averaging produced daily precipitation time-series consistent to disaggregated data (R2=0.85). The use of TRMM-enriched precipitation time-series for hydrological modeling of stream flow at Los Almendros watershed outlet, slightly improved a previous simulation in which only disaggregated precipitation dataset was used. When comparing simulated and observed data, the statistical fit coefficient improved from R2=0.64 (corresponding to only disaggregated precipitation data introduced into the hydrological model) to R2=0.68 (corresponding to TRMM-enriched precipitation data).

Sensitivity of Nutrient Estimations to Sediment Wash-off Using a Hydrological Model of Cherry Creek Watershed, Kansas, USA

This paper presents a hydrological and water quality model for Cherry Creek watershed, located in southeastern Kansas, USA. The Cherry Creek catchment drains approximately 88220 ha and it is a main contributor of water to the Neosho River. Hydrological modeling of the Cherry Creek watershed is performed using the Hydrological Simulation Program Fortran (HSPF). Simulated results for total ammonia (TAM) concentrations occurring at the Cherry Creek watershed outlet for four land use scenarios and a 2-year simulation period, are presented. Sensitivity analysis of total ammonia estimations (TAM=NH3+NH4) to the unbounded HSPF parameter POTFW is subsequently presented. POTFW represents the ratio of a water quality constituent yield to sediment wash-off outflow. Results showed that small perturbations to a 50 mg/Kg POTFW base value produce the largest normalized sensitivities. Peak sensitivities reached up to 248%, with the -1% perturbation producing the most dramatic sensitivity response in TAM estimations. Results showed a strong relationship between normalized sensitivities to river flow regime. Non-linearities in sensitivity for small ±1% perturbations were detected. These non-linearities are more evident for high stream flow values (strong flood events). For larger perturbations (±60%, ±40%, ±20%, and ±5%) the sensitivity response was shown to be linear.