Hydrologic Model of the Mayagüez Bay Watersheds: Progress Report Eric Harmsen, Associate Professor Dept. of Agricultural and Biosystems Engineering Marcel Giovanni Prieto, Graduate Student Dept. of Civil Engineering and Surveying

Acknowledgements NASA-EPSCoR NASA-EPSCoR US Geologic Survey US Geologic Survey Sea Grant Sea Grant U.S. Army Corps of Engineers (ERDC) U.S. Army Corps of Engineers (ERDC) LARSIP Laboratory LARSIP Laboratory Puerto Rico Water Resources and Environmental Research Institute Puerto Rico Water Resources and Environmental Research Institute Professor Nazario Ramirez, UPRM Professor Nazario Ramirez, UPRM Students: Sandra Ortiz, Richard Diaz, Moises Angeles Malaspina, Christian Calderon Students: Sandra Ortiz, Richard Diaz, Moises Angeles Malaspina, Christian Calderon

Some Water Issues in Puerto Rico  Water conflicts between agricultural and non-agricultural community (Lajas, PR)  Sediment transport is contaminating marine resources at numerous coastal areas in PR  Saltwater intrusion is threatening groundwater resources in the north and south coast of PR  Dropping groundwater elevations occurring in the South Coast.  Many of the principal reservoirs have become partially filled with sediment since their construction, reducing their effectiveness in providing water supplies and mitigating flood peaks.(e.g., Carraízo Reservoir which supplies San Juan)  Many of the principal reservoirs have become partially filled with sediment since their construction, reducing their effectiveness in providing water supplies and mitigating flood peaks. (e.g., Carraízo Reservoir which supplies San Juan) Problems with the water supply service of 700,000 families at the present time in the island (Nuevo Día 05 Feb. 2005)  Problems with the water supply service of 700,000 families at the present time in the island (Nuevo Día 05 Feb. 2005)

Sediment Discharge to the Mayagüez Bay Rio Grande de Anasco Outlet

Water related issues will become even more serious in the future Potential climate change Potential climate change Urban growth Urban growth Increasing population Increasing population Increasing cost of water and energy Increasing cost of water and energy Contamination of water supplies Contamination of water supplies Environmental impacts from changing flows Environmental impacts from changing flows

Objective To develop an integrated hydrologic model for the Mayaguez Bay Watersheds for the purpose of To develop an integrated hydrologic model for the Mayaguez Bay Watersheds for the purpose of Estimating the components of the hydrologic cycle Estimating the components of the hydrologic cycle Evaluate the water balance under climate change conditions (uncoupled) Evaluate the water balance under climate change conditions (uncoupled) Longer-term objectives: Apply an integrated hydrologic model coupled with a regional atmospheric model (e.g., RAMS/TOPMODEL) Apply an integrated hydrologic model coupled with a regional atmospheric model (e.g., RAMS/TOPMODEL) Evaluate the water balance for the entire island Evaluate the water balance for the entire island

Integrated Hydrologic Modeling

MOTIVATION We will be able to address scientific and practical questions related to the hydro/atmospheric system  How might changes in global/local weather affect our water supply  How will urban growth effect the hydrology (land use change, Urban Head Island effect)  Evaluate the effect of specific types of storms on  Flooding  Landslide potential

Modeling Strategy 1. Multi-watershed model (short-term) Develop and calibrate hydrologic modelDevelop and calibrate hydrologic model Use output from climate change simulations from an atmospheric simulation model as input to the hydrologic modelUse output from climate change simulations from an atmospheric simulation model as input to the hydrologic model 2. Island-wide model (long-term) Develop and calibrate hydrologic modelDevelop and calibrate hydrologic model Hydrologic model coupled with RAMSHydrologic model coupled with RAMS

Qualification Model will be developed based on a rough calibration Model will be developed based on a rough calibration Available groundwater elevationsAvailable groundwater elevations USGS gauging station – Total daily volume (not hydrographs)USGS gauging station – Total daily volume (not hydrographs) Overland flow only (no channel flow)Overland flow only (no channel flow)

Model Selection Requirements Should simulate Should simulate Overland flowOverland flow Vadose zone flowVadose zone flow Groundwater flow (preferably in 3-D)Groundwater flow (preferably in 3-D) 1-D channel flow1-D channel flow Should run on a supercomputer Should run on a supercomputer Source code should be freely available Source code should be freely available Models we evaluated: Mike She, WASH123D, IHM, GHSSA Mike She, WASH123D, IHM, GHSSA

Conceptual model developmentConceptual model development Identification of data sources Identification of data sources Delineation of study area Delineation of study area Conceptualize surface, soil and subsurface systems Conceptualize surface, soil and subsurface systems Development of GIS map Development of GIS map Perform simplified GIS water balance Perform simplified GIS water balance

Study Area Requirements Requirements Two or more watershedsTwo or more watersheds Boundary along coastBoundary along coast Large topographic reliefLarge topographic relief Include alluvial and bedrock aquifersInclude alluvial and bedrock aquifers Various land use categoriesVarious land use categories

GIS Water Balance of the Mayaguez Drainage Basin Precip = ET + RO + Rch +ΔS Precip = Precipitation ET = Evapotranspiration RO = Surface Runoff Rch = Aquifer Recharge ΔS = Change in soil moisture storage

Soil Moisture Content

Potential Evapotranspiration Hargreaves-Samani Method Hargreaves-Samani Method PET = x R a x (T +17.8) x (T max – T min ) 0.5 PET = potential or reference ET R a = extraterrestrial evapotranspiration T = average daily air temperature T min = average daily minimum temperature T max = average daily maximum temperature

Hydrologic Model - Evapotranspiration Surface Elevation Evaluation of Simplified Method Air Temperature Reference Evapotranspiration

Hydrologic Model - Evapotranspiration K c Literature Reference ET X Actual ET September NDVI Actual ET January

Hydrologic Model – Surface Runoff MONTHLY RUNOFF COEFFICIENT MONTHLY RAINFALL LAND COVER MONTHLY RUNOFF

Aquifer Recharge January Aquifer Recharge was zero at all locations September 59.7 mm Average

Global Warming

PET = x R a x (T +17.8) x (T max – T min ) 0.5 “ There has also been a general trend toward reduced diurnal temperature range, mostly because nights have warmed more than days.” - Union of Concerned Scientists - Union of Concerned Scientists global-warming-heat-waves.html

Global Climate Circulation Model – Caribbean Area DOE - Accelerated Climate Prediction Initiative

Some Climate Change Results

Conclusions from GIS Water Balance Analysis During the next 50 to 100 years: ET can be expected to increase by 3 to 5 mm/month ET can be expected to increase by 3 to 5 mm/month In the worse case the aquifer recharge will also drop by this amount In the worse case the aquifer recharge will also drop by this amount The expected drop in the water table is between 13 to 27 mm. The expected drop in the water table is between 13 to 27 mm. Increase urban development may decrease aquifer recharge and increase surface runoff. Increase urban development may decrease aquifer recharge and increase surface runoff.

Numerical Model MIKE SHE MIKE SHE AdvantagesAdvantages Easy to use Easy to use 3-D groundwater 3-D groundwater Water balance analysis tools are excellent Water balance analysis tools are excellent Can simulate other processes: sediment and solute transport Can simulate other processes: sediment and solute transport DisadvantagesDisadvantages Only runs on a PC Only runs on a PC Documentation is not complete Documentation is not complete OLF – Diffuse wave approximation of the Saint Venant equations UZ – Richards Equation, gravity method, 2 layer water balance SZ – standard groundwater equation (MODFLOW)

Simulation of average conditions for Mayaguez Bay Area Rainfall – Time series for Hacienda Constanza weather station Rainfall – Time series for Hacienda Constanza weather station Manning’s n: 0.07 Manning’s n: 0.07 Soil: Loamy Clay Soil: Loamy Clay Potential ET: 4.4 mm/day Potential ET: 4.4 mm/day Aquifer Aquifer type: unconfinedtype: unconfined thickness: 33 mthickness: 33 m conductivity: 0.33 m/dayconductivity: 0.33 m/day Initial groundwater elevation: 0 m below surface Initial groundwater elevation: 0 m below surface

Future Work Model Calibration Model Calibration Groundwater elevationsGroundwater elevations Daily Surface water VolumesDaily Surface water Volumes Climate Change scenarios Climate Change scenarios Decide which climate parameters to varyDecide which climate parameters to vary Write Proposals for more funding (NASA-NEWS) Write Proposals for more funding (NASA-NEWS)