1. HYDROLOGIC MODELING OF THE LOWER ALTAMAHA RIVER BASIN Multimedia Environmental Simulations Laboratory Georgia Institute of Technology June 2001

2. OUTLINE 1. Introduction 2. Distributed Hydrologic Modeling 3. Data Requirements 4. Integration with GIS 5. Lower Altamaha River Basin 6. Example Application

3. INTRODUCTION Hydrological modeling involves the mathematical simulation of the response (hydrograph) of an hydrologic unit (basin, watershed) to an hydrological event (precipitation) Classification of hydrologic models are based on: process description scale solution technique

4. PROCESSES Distributed Models Mixed Models Lumped Models Stochastic Models Deterministic Models Spatial dimensions (X, Y, Z) Combination No spatial dimension Entirely random Entirely physical Distributed Models Mixed Models

5. LUMPED SYSTEMDISTRIBUTED SYSTEM Watershed averaged data Lumped description Low maintenance Black-box Highly Empirical Pixel-based data Distributed description High maintenance White-box Highly physical Spatial non-uniformity High requirements for data & computer resources LUMPED vs. DISTRIBUTED MODELS

6. SCALE SPACE TIME 0-D 1-D 2-D 3-D Event Based Daily Monthly Yearly Event Based 3-D

7. SOLUTIONTECHNIQUE FINITE DIFFERENCE FINITE ELEMENT ANALYTICAL FINITE DIFFERENCE FINITE ELEMENT

8. Hydrologic Modeling SUBSURFACESURFACE Saturated Zone Flow Overland Flow Unsaturated Zone Flow Channel Flow Infiltration Interception-Evapotranspiration WATERSHED MODEL

9. WATERSHEDPROCESSES Overland Flow Processes Subsurface Flow Processes Contaminant Transport Output Governing Equations Initial and Boundary Conditions Inputs Conservation of Mass Conservation of Momentum Conservation of Energy typically discharge, contaminant concentrations Global Parameters Non-spatial Data Spatial Data

10. Precipitation data map Runoff data map Precipitation RunoffRunoff Regional Response Curve Hydrologic Function / Model MAP ALGEBRA MAP CALCULUS vs.

11. DATA REQUIREMENTS Main Data Structures Raster Vector Ref: D. Tarboton

12. Point Line Polygon Data TypeExampleVectorRaster Meteorological Station River, Road Watershed, City GIS REPRESENTATION

13. CategoryDescriptionSource Meteorology Land Use/Cover Soils Topography Stream flow Digital Elevation Models (DEM) (30 m or 100 m resolution) Satellite based land use/cover info USGS EROS Data Center GIS GA Clearinghouse USGS EROS Data Center GIS GA Clearinghouse State Soil Geographic Database (STATSGO) USDA National Weather Service Climatic Data (precp, temp…) NOAA River flows and stages USGS DATA SOURCES

14. LAND COVER/USESOILSTOPOGRAPHY Pixel scale attribute data Scale and resolution is not necessarily similar!!! Possible Other Data Sets RESAMPLING

15. INTEGRATION WITH GIS Strong links between distributed modeling and GIS Increased availability of large amounts of spatial data requires suitable processing software Data analysis (pre- and post- processing) Numerical models running under GIS Visualization MESL using ArcView and ArcInfo Auxiliary software (Remote Sensing and Image Processing - ENVI)

16. LOWER ALTAMAHA BASIN Entire Altamaha BasinEntire Altamaha Basin 3drains about 1/4 of Georgia 3formed by Ocmulgee + Oconee + Ohoopee 33rd largest basin draining to Atlantic Ocean Lower Altamaha BasinLower Altamaha Basin 3located at the most downstream point 3area A ~ 3,900 km 2 3long term average annual precipitation P ~ 45 inch 3long term average Q ~ 14,000 ft 3 /s 3average elevation E ~ 50 m

18. 3administratively divided by 10 counties 3agricultural activities dominate 3total population (Census 1990) watershed: 47,740 (0.7%) 10 counties: 185,144 (2.9%) Georgia : 6,478,149 0.7% 0.7% of Georgia population 3total land area watershed: ~ 3,900 km 2 (2.6%) 10 counties: ~ 11,265 km 2 (7.4%) Georgia: ~ 152,800 km 2 2.6% 2.6% of Georgia land

20. 3Shaded relief of region ---> Low lands of Georgia 3Topographically not complex but hydrologically is 3Highly vegetated 3Wetlands common in river banks & coastal region 3Forests and pasture in other portions 3Mostly pristine (compared to other parts of Georgia) 3Common soil types : Loam - Sand - Loamy Sand 3Agriculture dominated (Vidalia Onions) 3Forestry developed 3Main industrial establishments The Edwin Hatch Nuclear Power Plant (1630 MW) near Baxley Rayonier Pulp Mill at Jesup

21. The Edwin Hatch Nuclear Power Plant near Baxley on right side of Altamaha Rayonier Pulp Mill at Jesup on right side of Altamaha

22. Lowlands / Coastal Plains Transition Zone Highlands

24. 3Lower Altamaha river average slope ~ 0.00018 m/m 3Gently meandering nature 3Acts like a conduit with no significant drainage area 3150 km long corridor has an average width of 26 km 3No major navigation activity

25. Little OcmulgeeOcmulgee near Lumber City Altamaha near BaxleyAltamaha Delta

27. Typical River Channel Vegetation near Coastline Agricultural land recovered from forest vegetation in the backyard Forest Clear CutEutrophication in slow-running sections

29. EXAMPLE APPLICATION SCS Curve Number Method … runoff is a function of precipitation, initial abstraction and potential maximum retention where;Q : runoff (inch) P : precipitation (inch) S : potential maximum retention after runoff begins I a : initial abstraction (inch)

30. The parameter S is related to soil and cover conditions of watershed through an hypothetical parameter called CURVE NUMBER (CN). CURVE NUMBER is any number between 0 and 100 and is a function of: 3 Hydrologic Soil Group (A, B, C, D) 3 Land Cover Type 3 Land Treatment 3 Antecedent Moisture Condition (Dry, Wet, Average)

33. SCS-CN Application Initial Moisture Content Soil Type Grid Land Cover Grid Precipitation Grid Flow Grid PIXEL LEVEL DATA SETS Application is coded in C Integrated with ArcView v3.2a User-friendly GUI

34. Thank you...