runoff generation and sediment transport: do saturated zones play a role in tropical watersheds?
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Runoff generation and sediment transport: Do saturated zones play a role in tropical watersheds?TRANSCRIPT
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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
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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
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Infiltration
Evaporation
Soil moistureInterflow
Evapotranspiration
Recharge
Precipitation
Runoff
Runoff
Water table Evapotranspiration
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Rainfall intensity has to
exceed the soil’s infiltration
rate for Hortonian flow
4
0
2
4
6
8
10
0.00 0.20 0.40 0.60 0.80 1.00
Infiltra
tio
n c
ap
ac
ity
,
Ra
infa
ll In
ten
sity
(c
m/h
r)
Probability of Exceedance
Median infiltration rate
Minimum infiltration rate
Rainfall intensity curve
Bayabil et al., 2010
Mecanism:
-Hortonian(Horton, 1933)
-Dunnean
(Dunne and Black, 1970,
Kirkby, 1969
Freeze, 1972
Dunne et al., 1975)
MAYBAR, ETHIOPIA
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5Sediment concentration data
exhibit variable but particular
underlying patterns
Inst
alla
tio
n o
f te
rra
ce
s
Cw = AcacPce• Rd 0.4
Weirs
Terraces
C = a• Q n
Guzman et al., 2013; Steenhuis et al., 2014 ANJENI, ETHIOPIA
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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
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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
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Objectives
How do spatial and temporal
patterns reveal which dynamics are
present?
8
Middle
Upper
Lower
R² = 0.6235
0
2
4
6
8
10
12
14
25
-Ju
n
15
-Ju
l
4-A
ug
24
-Au
g
13
-Se
p
Se
dim
en
t C
on
ce
ntr
atio
n (
g L
-1)
Mean daily sediment
concentration
D.C. Dagnew, 2013DEBRE MAWI, ETHIOPIA
COLOMBIA
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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
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Methods 10
Rio Bolo
Micro-cuenca
La Vega
The Nature Conservancy
Fondo Agua por La Vida y La Sostenibilidad, Asobolo, Asocaña, Cenicaña
AGUACLARA, COLOMBIA
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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
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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
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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
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14Analysis: Broad scale
Tilahun et al., 2014 AGUACLARA, COLOMBIA
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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
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16
-3.20
-2.70
-2.20
-1.70
-1.20
-0.70
-0.20
25-Jul 4-Aug 14-Aug 24-Aug 3-Sep
Wat
er t
able
dep
th b
elow
surf
ace
(m)
Downslope w/o Gully
Midslope-1
Midslope-2
Upslope
8
9
16
1
Midslope-1
Midslope-2
Upslope
Downslope Weir
Analysis: Coupling scales
1. Conceptualization of hydrology
2. Generate localized patterns of soil loss on hillslope and land use areas
DEBRE MAWI, ETHIOPIA
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Analysis: Critical concepts
4. Comparison of pattern representation with modeling NSE , RMSE, GLUE
17
AGUACLARA, COLOMBIA
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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
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Future work
Study ecosystem services in greater
detail
Develop modeling alternatives
Replicate study
19
AGUACLARA, COLOMBIA