Hydrological modelling in the context of land use change and climate change Emil A. Cherrington Research Associate, CATHALAC

Revisión general 1.Overview: ERI CaribSave project 2.Theory: Water balance 3.Q & A

Environmental Research Institute-University of Belize CATHALAC

Land Cover Scenarios source: WRI / ICRAN-MAR (2006)

 Project duration: Feb – Sept (18 months)  Location: Belize’s watersheds, including trans- boundary areas in Mexico, Guatemala Mexico Guatemala

Mexico Guatemala Determine the current demand for and supply of water in Belize’s major and minor watersheds Determine the current demand for and supply of water in Belize’s major and minor watersheds Assess future supply and demand against the range of future land use scenarios and future CC scenarios Assess future supply and demand against the range of future land use scenarios and future CC scenarios Examine how water quality might change as a result of CC and land use change scenarios Examine how water quality might change as a result of CC and land use change scenarios

Image credit: Jason Tullis II. Theory: Hydrological modelling

Among others: HEC-HMS con HEC-RASHEC-HMS con HEC-RAS SWAT (ArcSWAT / MapWindow SWAT)SWAT (ArcSWAT / MapWindow SWAT) KinerosKineros AGWAAGWA N-SPECT / OpenNSPECTN-SPECT / OpenNSPECT WEAPWEAP InVESTInVEST Available platforms

Runoff + erosion as part of the hydrological cycle Characteristics related to the soil, land cover / land use, topography, and rainfall determine the runoff. source: NOAA CCAP

Influence of land cover on erosion source: L. Buffett (2012)

Required data inputs for modelling Land use / land coverLand use / land cover Digital elevation model (DEM)Digital elevation model (DEM) Soil typeSoil type –USGS hydrological group –Soil erodibility (K factor) –Other parameters Climate data (e.g. rainfall, temperature)Climate data (e.g. rainfall, temperature)

Modelling with SWAT Model outputs 1.Evapotranspiration 2.Infiltration 3.Aquifer recharge 4.Runoff 5.Stream flow 6.Erosion source: Neitsh et al. (2011)

Other results Areas of high vulnerabilityAreas of high vulnerability –Identification of the areas which contribute most to sediment loads / areas which lose most of their soils –Quantification of the area (e.g. in hectares or km 2 ) at risk per sub-watershed / basin Sediment accumulationSediment accumulation –Identification of the sections of rivers which receive the most sediments –Medida de densidad de sedimentación por área de subcuenca

Main N-SPECT functions Runoff modelRunoff model –U.S. Soil Conservation Service (SCS) curve number technique Erosion modelErosion model –Universal soil loss equation (USLE) Event: Modified (MUSLE)Event: Modified (MUSLE) Annual: Revised (RUSLE)Annual: Revised (RUSLE) Contaminant modelsContaminant models –Using concentration coefficients NOAA CCAP

Soil curve numbers in N-SPECT

24 Methods (pt1) Stream ‘burning’ using data on river network locationsStream ‘burning’ using data on river network locations –This is to assure adequate flow calculations, despite potential / likely errors in the digital elevation models (DEMs) Filling DEM to remove false depressions (sinks)Filling DEM to remove false depressions (sinks) –This step is necessary to ensure that flow calculations function (i.e flow direction, flow accumulation exercises) Spatial hydrology basics

Methods (pt2) Flow directionFlow direction –only 8 possible routes Flow accumulationFlow accumulation (based on the flow direction routine) 1 –Based on the DEM, this will show the approximate hydrological network 1 ArcGIS Desktop Help Calculating flow accumulation. Hydrology (Spatial Analysis). webhelp.esri.com Spatial hydrology basics

26 Estimating erosion using the USLE method Focused on the production / concentration of sedimentFocused on the production / concentration of sediment USLE = Universal Soil Loss EquationUSLE = Universal Soil Loss Equation Annual & Event-based (RUSLE & MUSLE)Annual & Event-based (RUSLE & MUSLE) RUSLE: A = R * K * L * S * C * PRUSLE: A = R * K * L * S * C * P Where:Where: –A = quantity of soil lost in a year –R = rainfall erosivity factor –K = soil erodability factor –L = slope length factor –S = slope steepness factor –C = cover management factor –P = supporting management practices factor

III. Q & A