CVEN 689 Instructor: Dr. Francisco Olivera Estimating Salt Concentration at Ungaged Locations from Parameters derived using GIS Ganesh Krishnamurthy Water Resources Engineering

Objectives To become proficient in ArcView 3.2 To prepare an empirical model to predict salt concentrations at ungaged locations using GIS

Why is this Important? Though water is diverted, the quality is not considered Diversions often occur from ungaged locations where the salt concentration is unknown

Datasets used Grid: USGS 1-Degree DEM (1:250,000) Grid: U.S. Curve Number Grid: U.S. Mean Annual Precipitation Lines: EPA RF3 and NHD Channel Lines (1:100,000) Points:USGS Control Point Locations Naturalized Salt Data at all gaging stations in the Brazos River Basin

WRAP Parameters and Tools Menu

Correcting the Stream Network Stream network with loops and braids Corrected Stream network without loops and braids

Burning the Stream Network BRAZOS DEM STREAM NETWORK BURNED DEM

Making the Flow Direction and the Flow Accumulation Grids FILLED DEM FLOW DIRECTION FLOW ACCUMULATION

The CN and the Mean Annual Precipitation Grids The CN Grid The Mean Precipitation Grid

Stream Network Questions??? Control point locations will match exactly to channel grid cells in the flow accumulation grid. The outlet locations in the flow accumulation grid are correctly defined. Downstream control points can be identified.

Attribute Table

Control Point Parameters

Assumptions

Empirical Equations

Models Model 1- uses the Area Ratio Parameter Model 2- uses the Area-Precipitation Ratio Parameter Model 3- uses the Area-Precipitation-CN Ratio Parameter All three models have been applied to the following pairs of control points in the Brazos Basin for the years : CPID , CPID CPID , CPID CPID , CPID

Results and Discussion R 2 = 0.97

Results and Discussion R 2 = 0.82

Results and Discussion R 2 = 0.71

Results and Discussion R 2 = 0.67

Results and Discussion  The r 2 values obtained for the different models range between 0.48 and 0.91 for the period  The closest fit is observed for the year 1977 for all the three models with an average r 2 value of 0.97 for all five years.  The average of the r 2 values for the 6 years for all three models is 0.69

Conclusions  The deviations in the observed values and the predicted values can be attributed to : parameters that affect salinity other than the ones considered in the assumption Computational Errors in estimating naturalized salt concentrations at gaged locations The model uses a monthly time scale, whereas sub monthly events like thunderstorms are not considered

Future Work  To identify the “missing” parameters to improve the relation between the observed and the predicted values  To test run the model in WRAP for the Brazos river basin.

QUESTIONS