Indrajeet Chaubey
Purdue University
ichaubey@purdue.edu
Water Quality Modeling
Food, Energy, Water Workshop
https://engineering.purdue.edu/ecohydrology
October 12, 2015
Iowa State University
Remote Sensing Based Inputs
In Situ Input
Weather,
Vegetation Vigor
Soil Moisture
Multiscale Models
Field Scale
Model 1
Site Output
Database
Downloadable
Databases
Weather Data
Field Scale
Model 2
Watershed
Scale
Regional Scale
Models
Models
Soil Data
Regional Scale
Models
Crop Data
Weather Simulation Data
https://engineering.purdue.edu/ecohydrology
Weather/Climate
Landscape & Hydrology
Precipitation
Transpiration
(from plants)
Evaporation (from leaves
and bare soil)
Corn
Runoff
Infiltration
Grass
Runoff
Plant Uptake
Tile Drains (if applicable)
Percolation
Lateral Flow
Return Flow
Deep Percolation
Groundwater
https://engineering.purdue.edu/ecohydrology
Ditch/
Stream
Landscape & Nitrogen
Precipitation
Fertilizer
Volatilization
Trapped by
Filter Strip
Nitrogen loss with
soil erosion
Grass
Corn
Infiltration
(Nitrate)
Tillage
Runoff
Plant Uptake
Tile Drains (if applicable)
Percolation
(Nitrate)
Deep Percolation
(Nitrate Leaching)
Lateral Flow
(Nitrate)
Some organic N is attached to
eroded soil particles and nitrate
(NO3-) is dissolved in water
https://engineering.purdue.edu/ecohydrology
Nutrient Cycling
Sw
Sb
Sp
Water
Benthic zone
Sediments
Complete cycle = spiraling length
Spiraling length (S) = uptake length (Sw) + turnover length (Sb+Sp)
C
Q C 1  
C 
1


AD
 kcC  k B C B


t
A x A x 
x 
h
(Advection)
(Dispersion)
(Uptake)
https://engineering.purdue.edu/ecohydrology
(Release)
Water quality modeling– Wildcat Creek Watershed
Cibin et al., 2011
https://engineering.purdue.edu/ecohydrology
6
Perennial bioenergy crops improve water quality
• Bioenergy crops grown on marginal Lands
https://engineering.purdue.edu/ecohydrology
7
Perennial bioenergy crops improve ecosystem
services
St Joseph river watershed
High slope area: 347 Km2(33% of corn/soybean area and 12% of watershed area)
Fresh water provision (FWPI) , food (FPI) and fuel provision (FuPI),
erosion regulation
8
https://engineering.purdue.edu/ecohydrology
(ERI), and flood regulation (FRI) based on Logsdon & Chaubey, 2013
Crop placement optimization - example
•Objective Functions:
•maximize biomass
production
•Minimize erosion,
nitrate losses
•Constraints:
•Grain yield reduction
< 10%
•Total biomass
production to support
>100 million gallon
ethanol
•At least 20% of
biomass from
switchgrass
•Stover removed from
slopes < 2%
https://engineering.purdue.edu/ecohydrology
Effects of climate change on hydrology
• Projected decrease in snowfall, cover and depth
• Rainfall is projected to increase
• Altered streamflow timing and amount
– Earlier spring peak flows
– Increase in flash floods and high flows
– Decline in summer seasonal streamflow
• Increase risk of summer moisture stress
• Temperature in projected to increase
•
– Longer growing season
– Longer period for growth
– Increase evapotranspiration
Intense rainfall events
– soil erosion
– Runoff process
https://engineering.purdue.edu/ecohydrology
Climate change impacts on ecohydrologic
processes
Miscanthus in high slope marginal land- St. Joseph River watershed
Flow
(m3/s)
Sediment
(Mg/ha)
Org N
(kg/ha)
Org P
(kg/ha)
Nitrate-N
(kg/ha)
Min P
(kg/ha)
 Results that are similar under all climate periods and GCMs (error
bars) show that water quality benefits due to land use change is
generally greater than the effects of climate change variability.
https://engineering.purdue.edu/ecohydrology
11
Future Research Needs
1. Experimental data at multiple spatial and temporal
scales
2. Improvements in the current watershed models to
include ecohydrologic process representation
3. Climate change impacts on catchment scale
ecohydrologic processes
4. Threshold effects
https://engineering.purdue.edu/ecohydrology