Runoff generation and sediment transport: Do saturated zones play a role in tropical watersheds?

1. Runoff generation and
sediment transport:
Do saturated zones play a role in
tropical watersheds?
CHRISTIAN DAVID GUZMÁN
PHD CANDIDATE, CORNELL UNIVERSITY
FOOD SYSTEMS AND POVERTY REDUCTION IGER FELLOW
NSF/USAID RESEARCH AND INNOVATION FELLOW
26 NOVEMBER 2014

2. Motivation
 Soil and water conservation is a multi-actor
unresolved solution
 Heavy sediment loads reveals symptoms
 Sustainability requires a focus on processes in
the Andean climate, specifically:
 1. Main underlying flow patterns
 2. Sediment concentration patterns and
variability
2
CALI, COLOMBIA

3. Infiltration
Precipitation
Evaporation
Soil moisture
Evapotranspiration
Interflow
Recharge
Runoff
Runoff
Water table Evapotranspiration

4. Rainfall intensity has to
exceed the soil’s infiltration
rate for Hortonian flow
4
10
8
6
4
2
0
Median infiltration rate
Rainfall intensity curve
Minimum infiltration rate
0.00 0.20 0.40 0.60 0.80 1.00
Infiltration capacity,
Rainfall Intensity (cm/hr)
Probability of Exceedance
Bayabil et al., 2010
Mecanism:
-Hortonian
(Horton, 1933)
-Dunnean
(Dunne and Black, 1970,
Kirkby, 1969
Freeze, 1972
Dunne et al., 1975)
MAYBAR, ETHIOPIA

5. 5
Sediment concentration data
exhibit variable but particular
underlying patterns
Installation of terraces
Cw = Acac
Pce• Rd 0.4
Weirs
Terraces
C = a• Q n
Guzman et al., 2013; Steenhuis et al., 2014 ANJENI, ETHIOPIA

6. Runoff generation and sediment
transport dependent on storage
capacity
Hillslope
Degraded
Saturated
infiltration
interflow
overland flow
(Cappus, 1960,
Kirkby, 1969; Freeze, 1972;
Dunne and Black, 1979; Beven, 2000; Buytaert et al., 2007;
Collick et al., 2009; Steenhuis et al., 2013; Tilahun et al., 2014)
ANDIT TID, ETHIOPIA

7. Objectives
 Short term: detect runoff and sediment
transport patterns in Aguaclara watershed
network
 Mid term: build supporting evidence for a
well defined runoff mechanism hypothesis
 Long term: study hydrological and
geomorphological patterns in the Andes for
conservation adjustment
7
COLOMBIA

8. Objectives
 How do spatial and temporal
COLOMBIA
patterns reveal which dynamics are
present?
8
Upper
Middle
Lower
R² = 0.6235
14
12
10
8
6
4
2
0
25-Jun
15-Jul
4-Aug
24-Aug
13-Sep
Sediment Concentration (g L-1)
Mean daily sediment
concentration
DEBRE MAWI, ETHIOPIA D.C. Dagnew, 2013

9. Questions
 1. Which runoff generation mechanism is
dominantly present in a representative
watershed?
 2. Which areas of the site might be sediment
source areas?
 3. Is there a correlation between soil loss and
nutrient loss?
 4. Which hydrological and pedological dynamics
can be adjusted for improved runoff and
sediment transport estimation?
9
CALI, COLOMBIA

10. AGUACLARA, COLOMBIA
Methods 10
The Nature Conservancy
Fondo Agua por La Vida y La Sostenibilidad, Asobolo, Asocaña, Cenicaña
Rio Bolo
Micro-cuenca
La Vega

11. Methods
 1. Characterization of flow patterns and sediment
and nutrient export
 Rainfall intensity vs infiltration capacity (Double ring
infiltrometer, Constant head permeameter)
 Monitoring hydrological balance
 Monitoring sediments and water
 2. Spatial and temporal changes in the micro
watershed
 Soil surface changes
 Water table depths
11
AGUACLARA, COLOMBIA
DEBRE MAWI, ETHIOPIA

12. Methods
 3. Soil nutrient status and relation to soil
loss patterns (0-15 cm)
 Macronutrients (nitrogen, potassium, phosphorus)
 Exchangeable Cations
 pH, organic matter
 4. Comparison of patterns
 PED, TOPMODEL
 InVEST, RIOS
 SWAT
12
AGUACLARA, COLOMBIA

13. Analysis: Broad scale
 1. Conceptualization of hydrology
 Flow reservoir transfer
 (Thornthwaite-Mather, 1955)
 Nash-Sutcliffe Efficiency
 Conceptualization of sediment transport
 Stratification of data (cumulative
effective precipitation; Lui et al., 2008)
 Non-parametric statics, ej. Kruskal-
Wallis, Wilcoxon Rank Sum
13
AGUACLARA, COLOMBIA

14. Analysis: Broad scale 14
Tilahun et al., 2014 AGUACLARA, COLOMBIA

15. Analysis: Localized scale
 2. Generate localized patterns of soil
loss on hillslope and land use areas
 Upslope vs downslope, etc.
 Grazing vs forests, etc.
 3. Compare nutrient status and
change patterns with soil depth
changes
 Coefficient of determination, R2
 Correlation coefficient, Pearson r
15
AGUACLARA, COLOMBIA

16. 16
Analysis: Coupling scales
Midslope-2
25-Jul 4-Aug 14-Aug 24-Aug 3-Sep
-0.20
-0.70
-1.20
-1.70
-2.20
-2.70
-3.20
16
9
Water table depth below
surface (m)
Downslope w/o Gully
Midslope-1
Midslope-2
Upslope
8
1
Midslope-1
Upslope
Weir Downslope
1. Conceptualization of
hydrology
2. Generate localized
patterns of soil loss on
hillslope and land use
areas
DEBRE MAWI, ETHIOPIA

17. Analysis: Critical concepts
 4. Comparison of pattern
representation with modeling
 NSE , RMSE, GLUE
17
AGUACLARA, COLOMBIA

18. Expected outcomes
 1. Preliminary integration of runoff concepts
 2. Identify areas or land uses that generate
runoff and sediment
 3.Identify the simple or complex relationship
between soil loss and nutrient changes
 4. Evaluation of model performance*
18
Horton, 1933; Dunne and Black, 1979 AGUACLARA, COLOMBIA

19. Future work
 Study ecosystem services in greater
detail
 Develop modeling alternatives
 Replicate study
19
AGUACLARA, COLOMBIA

20. Thank you!
cdg65@cornell.edu
20
COLOMBIA ETHIOPIA
Montgomery, 2007