Pothole Microwatershed
Modeling and Data
Management
GIS Certificate
Ligia de Oliveira Serrano
MS Student – Agricultural and Biosystems Engineering
MS Adviser: Amy Kaleita
April, 2015
Potholes
What is the problem?
Introduction
• Potholes
Why to study/ model?
Hydrological impacts of potholes
Generate more information
• Enclosed depressions;
• Formed in recent glaciated
landscapes
• Common in Iowa / flat terrain
• Potential Impacts:
• Flood Control; water quality
improvement
• Pothole Classification:
• Land cover – prairie vegetation
• Soil properties - hydric
• Topography - depression
How to study?
Watershed
Models
Introduction -Watershed Models
• Watershed Models: Attempt to replicate environment phenomenon’s
• Evapotranspiration, runoff, infiltration, etc
• AnnAGNPS – Annualized Agricultural Non-Point Source Model
• Able to model potholes
• Requires different GIS Datasets – landcover, soil, Elevation (Digital Elevation
Model), weather,…;
• Watershed characterization
• Generates the drainage areas associated with an outlet;
• For potholes: microwatersheds
• Create hydrological units;
• Response units – specific landcover, soil, runoff pattern;
• Estimates Hydrology, Nutrient, Sediment loads
This project:
Pothole Hydrology
-
Water balance
(Volume variation)
Introduction - Hydrology
• Hydroperiod – number of days of flood per year / growing season
• Water regime – frequency, duration, and depth of flooding
• Impacts
• Downstream flood control - can act like a sponge for incoming flow
• Potential source of groundwater recharge
• Water Quality - treatment & filtering system for polluted water
Hydrology of individual potholes
 Effect in watershed scale?
Objective
• Assess prairie potholes in two different scales
• Watershed scale: Pothole area and volume in Walnut Creek watershed
• Pothole scale:
• Microwatershed characterization
• Estimation of pothole volume and area, as well as their
• Hydrology, with AnnAGNPS before and after land cover correction
• Infer the impacts of the hydrology of the watershed by the assessed of an
individual feature.
• Determine differences in AnnAGNPS results before and after land cover
correction for retired condition for the total simulation (1992 – 2014).
Spatial Question
• What are potential impacts of small depressions (potholes) in the
hydrology of a watershed with high pothole density?
• What are the impacts of GIS data correction in hydrological models
and the impact in a larger scale?
Methods
• How can we identify potholes?
• Bare and Filled DEM
High x Low Resolution DEM
• Fills sinks in the surface  Guarantee flow
• Differences  Depressions
• Pothole Criteria Land cover + Soil
 Modified
• Depressions
• With at least ¼ of an acre (~1012 m)
• Max Depth: 5 ft (~1.5 m)
• Volume Storage:
• High Resolution Digital Elevation Model
(DEM) generation
Terrain Generation  Lidar
• 1-meter resolution
• Surface Volume each 0.1 m
Low
High
Process
Lidar Points – LAS (Source)
LAS to Multipoint  Build Terrain (3D Analyst)  Terrain to Raster (DEM)
Digital Elevation Model (DEM) – Bare DEM
Fill (Spatial Analist)
Filled DEM
Minus(Filled DEM – Bare DEM) + Reclassification (Spatial Analyst)
Depressions (Raster)
Raster to Polygon (Spatial Analyst)
Depressions (Vector)
Extract by Mask from BareDEM (Spatial Analyst)
Large
Scale
study
Single Depressions (Raster)
Volume and Area Calculator (3D Analyst)
Model Validation – 1992 to 2014
Nash Surclife Index (Not GIS) – 2010 and 2011 (Logsdon, 2015)
Model Input Modification
Clip + Erase + Merge (Analysis and Data Management )
Small
Scale
study
What are the impacts?
Terrain Generation  Lidar
• Lidar : Light Detection and Ranging
• Remote Sensing method that uses light in the form
of a pulsed laser to measure ranges (variable
distances) to the Earth
• measurements of the ground, vegetation, and buildings
• Benefits:
• Store and manage vector-based terrain information in the
geodatabase  Boundary
• Collections can reach into the billions of points.
• Terrain pyramids enable appropriate subsets, based on area
of interest and accuracy requirements  Area information
• High-quality interpolation designed to handle a wide
variety of input data types.
• Etc...
Watershed Scale –
Walnut Creek
Watershed
Results
• Number of Potholes
• Criteria: ¼ acre (1012 sq-m) and depth 0.33 – 5 ft (0.1 – 1.5 m)
• Number of Potholes: 1030
• Depressions: Volume and area for all depressions
• 259 to 321.9 m in elevation
• Total area: ~ 3 thousand acres (13*10^6 m2)
• Volume: ~ 160 thousand ac-ft (2*10^8 m3)
• Individual Depressions
• Area
• Max: 90 acres (365 thousand m2 )
• Min: 1/4 acres (1012 m2)
• Volume
• Max: 312.14 to 313.44 m elevation ~ 4.3 ft (1.3 m depth)
• Vol: 162 ac-ft (200 *10^3 m3)
• Min: insignificant volume
• Potholes Located in watershed boundaries
• Walnut Pothole:
• Area: 7 acres
• Volume: ~9 acre-ft (11 thousand m3)
• 110 features larger (~10%)
• 920 features smaller
Pothole
Scale:
• Worrell Pothole:
Case
• Area: 14 acres
Study
• Volume: ~25 acre-ft (30 thousand m3)
• 48 features larger (~5%)
• 982 features smaller
Correction of geographical inputs
• Land Use
• Compare current and conserved conditions  Change in land
cover
• Management in the AnnAGNPS cells is determined according with
the predominant condition.
• Cell with 20% Corn, 20% Soybeans, and 60% Retire  100% RETIRE by
AnnAGNPS, predominant condition.
• Soils : In conserved conditions – wetland extension: Hydric soils
• Challenge: Make sure the actual area is converted to retire
• Why? Generation of robust results
Volume
Worrell
Walnut
Results – Volume Storage
• Walnut Pothole:
• Worrell Pothole:
• Area: 7 acres
• Volume: 11 thousand m3 (~9 acre-ft)
• Area: 14 acres
• Volume: 30 thousand m3 (~25 acre-ft)
Walnut Volume Storage
Worrell Total Volume Storage
311.0
312.2
312.1
310.8
312
310.6
311.8
311.7
Depth (m)
Depth (m)
311.9
y = -4E-09x2 + 0.0001x + 311.44
R² = 0.9826
311.6
310.4
310.2
y = -6E-10x2 + 5E-05x + 309.89
R² = 0.9816
311.5
310.0
311.4
311.3
309.8
0
2000
4000
6000
Volume (m3)
8000
10000
12000
0
5000
10000
15000
20000
Volume (m3)
25000
30000
35000
40000
Results - Hydrological Models
AnnAGNPS generates
consistent results 
Move to retire
condition
• Model Validation - 2010 and 2011: Current Condition
• Nash & Sutcliffe index (NSE) - Model Performance
•
•
•
•
Estimation of agreement between observed vs. simulated data
Hydrology studies
Pothole - year
Value variation: -1 to 1
Walnut
Reasonable values: NSE > 0
Worrell
Worrell, total simulation
1.2
1.2
1
1
0.8
0.8
Water Depth (m)
Water Depth (m)
Walnut, total simulation
0.6
0.4
0.2
0
5/1/2010
NSE index
0.87
0.90
0.6
0.4
0.2
8/9/2010
11/17/2010
2/25/2011
6/5/2011
9/13/2011
0
5/1/2010
8/9/2010
11/17/2010
Dates
Observed
Simulated
2/25/2011
Dates
Observed
Simulated
6/5/2011
9/13/2011
Current Management:
Conserved
Management:
CSCS:Corn-Soybeans
Corn-SoybeansRotation
Rotation
CSCS:
SCSC:Soybeans-Corn
Soybeans-CornRotation
Rotation
SCSC:
Retire/Grass: Conserved Areas
How to Correct?
• Divide the within
pothole in different
managements/soils
• Update Number of cells
• Update Soil type 
Hydric
• Modify input cells and
Run the AnnAGNPS
BeforeXAfter
GIS Correction
• Cells in
AnnAGNPS
• Soil
• Land Cover
Before X After GIS Correction
• Walnut
• After interpolation: 4 out of 11
cells considered to retire
• Pothole Area: ~7 acres (~3
hectares)
• AnnAGNPS Retire Area: ~6 acres
(~2.3 hectars)
Less area
• Worrell
conversion
• After interpolation: 12 out of 49
cells considered to retire
• Pothole Area: ~14 acres (~5.5
hectares)
• AnnAGNPS Retire Area: ~12 acres
(~4.0 hectares)
Less area
conversion
Does it correspond to observed condition?
Results - Walnut
1
1
20000
0.8
0.8
Depth (m)
1.2
Volume (m3)
Depth (m)
1.2
25000
0.6
15000
0.4
0.2
10000
0.2
0
Jan-92
Feb-95
Feb-98
Mar-01
Mar-04
Mar-07
Mar-10
0
Jan-92
Mar-13
Less water is being stored in Walnut pothole
0.6
0.4
0
Feb-92
5000
Walnut After
Walnut water-balance volume
Walnut Before
Jan-95
Jan-98
Jan-01
Jan-95
Jan-07
Feb-10
Feb-13
Date
Date
Depth (m)
Jan-04
Depth (m)
Overflow Height
Jan-98
Jan-01
Jan-04
Jan-07
Overflow
Feb-10
Feb-13
Date (Month-Year)
Walnut Before
Walnut After
168 less days producing runoff, smaller water accumulation in pothole.
Results - Worrell
Worrell water-balance difference volume
Worrell Before
50000
1.2
1.2
45000
1
1
Worrell After
Water Depth (m)
40000
Volume (m3)
Water Depth (m)
0.8
35000
0.6
30000
25000
0.4
20000
0.2
15000
0
10000Jan-92
0.6
0.4
0.2
Jan-95
Jan-98
Jan-01
Jan-04
Jan-07
Feb-10
0
Jan-92
Feb-13
Jan-95
Jan-98
Jan-01
Depth (m)
Jan-95
Jan-04
Jan-07
Feb-10
Feb-13
Date
Date
5000
0
Jan-92
0.8
Depth (m)
Overflow Height
Jan-98
Jan-01
Overflow
Jan-07
Feb-10
Feb-13
Less
water
is
being
stored
in
Worrell
pothole
Date (Month-Year)
Jan-04
Worrell Before Fix
Worrell After Fix
164 less events producing runoff, smaller water accumulation in pothole.
Volume Storage Difference
• Walnut: Events stored up to 4 thousand m3 (~3 acre-ft) more
• Sum: 1.6 * 10^6 m3 (1.3*10^3 acre-ft)
• Worrell: Events store up to 16 thousand m3 (~13 acre-ft) more
• Sum: 4.7 * 10^6 m3 (3.8*10^3 acre-ft)
Walnut Volume Difference
Worrell Volume Difference
4000
18000
3500
16000
14000
12000
2500
Volume (m3)
Volume (m3)
3000
2000
1500
8000
6000
1000
4000
500
0
Jan-92
10000
2000
Jan-95
Jan-98
Jan-01
Jan-04
Date
Jan-07
Feb-10
Feb-13
0
Jan-92
Jan-95
Jan-98
Jan-01
Jan-04
Date
Jan-07
Feb-10
Feb-13
Conclusions
• What is the impact of small depressions (potholes) in the hydrology of
a watersheds?
• These can store up to 25 acre-ft (Worrell)
• Can have an impact in flood control and water quality
• What are the impacts of GIS data correction in hydrological models?
• It is important to correct GIS data in a small scale
• Up to 13 acre-ft difference of water volume generation per event (Worrell)
• The assessed potholes do not consist of a good representation of the
potholes in the watershed  relatively big
Further Improvement/ Research
• Develop a more automated way to investigate individual features
• AnnAGNPS considers the potholes to be flat
• Linear relation between volume and water depth
• Area increases with water depth
• Calibrations needed
Pothole Model
Consideration
Pothole Reality
Thank you!
• Questions??