routing

GenRiver 1.0Distributed process-based model

spatial scale: 1-1000 ha,temporal scale: daily

Can be used as a tool to explore our understanding of historical changes in river flow due to land use change

stem-flow

through-fall

rainfall cloudinterception

lateral

outflow

percolation

rechargeinfiltration

surfaceevaporation

transpiration

canopy waterevaporation

uptake

baseflow

{

surface run-on

sub-surfacelateral

inflow

surface run-off

Quick flow

Trees

Soil

Hydrological functions of forest:

Landscape drainage

?

PES

RegulationSpatial planning

‘Permanent’ site characteristics Upland land use

Watershedfunctions

Downstream water users & stakeholders

Riverbed engineering

poverty

poverty

poverty

poverty

Watershedfunctions

1. Transmit water

2. Buffer peak rain events

3. Release gradually

4. Maintain quality

5. Reduce mass wasting

Site cha- racteristics

• Rainfall

• Land form

• Soil type• Rooting

depth (natural vegetation)

Relevantfor

• Downstream water users,

• esp. living in floodplains & river beds,

• esp. without storage

• or purification• at foot of slope

stem-flow

through-fall

rainfall cloudinterception

lateral

outflow

percolation

recharge

infiltration

surfaceevaporation

transpiration

canopy waterevaporation

uptake

quick-flow

baseflow

{

surfacerun-on

sub-surfacelateral

inflow

surfacerun-off

Stream:

GenRiver 1.0a simple model that translates a plot-level water balance to landscape level river flow

Land cover influences:

* evapotranspiration -> water yield (immediate)

* infiltration (medium term ~ soil type)

3. Subsurface flow into streams: ‘interflow’ or ‘soilquickflow’

1. Interception & evaporation from wet surfaces

5. Gradual release to streams through deep soil pathways

2. Overland flow into streams: quickflow

4. Uptake by plants for transpiration (+ soil evaporation)

14

2

3

5

Unit hydrograph – what happens to an ‘average’ drop of rainfall?

The core of the model :

Patch level represent daily water balance, driven by local rain rainfall and modified by land cover and soil properties of the patch

The patch can contribute to three types of stream flow :

1. Surface quick flow – on the day of rain event

2. Soil quick flow – on the next day after rain event

3. Base flow – via gradual release of groundwater

3. Subsurface flow into streams: ‘interflow’ or ‘soilquickflow’

1. Interception & evaporation from wet surfaces

5. Gradual release to streams through deep soil pathways

2. Overland flow into streams: quickflow

4. Uptake by plants for transpiration (+ soil evaporation)

14

2

3

5

Unit hydrograph – what happens to an ‘average’ drop of rainfall?

1. Interception & evaporation from wet surfaces 1

Step 1 – canopy interception

Rainfall per event, mm

Water storage on leaf sur- faces, mm

Capacity limitedThr

ough

fall

prob

abili

ty1:1

Current LAI

Waterfilm thickness

Will evaporate within a day

=Cap*(1-EXP(-Rain/Cap))

Calder (2004) HYLUC

1. Interception & evaporation from wet surfaces

2. Overland flow into streams: quickflow

1

2

Step 2 – Lack of Infiltration => overland flow

Two conditions lead to overland flow:

•Surface infiltrability less than required during storm (‘Hortonian’ overland flow, ‘sealing’ of the surface’); slope, surface roughness and rainfall intensity determine the time available for infiltration

•Saturation-limited: surface soil layers are saturated and rate of outflow determines possible rate of inflow

Rain duration,Can.Interc.DelaySurface staorage,

Slope SoilSat - Actual

PotInfRate

3. Subsurface flow into streams: ‘interflow’ or ‘soilquickflow’

1. Interception & evaporation from wet surfaces

2. Overland flow into streams: quickflow 1

2

3

Step 3 – Soil quickflow: drain towards ‘field capacity’

SoilQuickFlow: Max(0,Soil- FieldCap)

Saturation

SaturationGW store

Percolation Fraction

GW release Fraction Baseflow

FC

‘Two-tank model’

RootZone store

3. Subsurface flow into streams: ‘interflow’ or ‘soilquickflow’

1. Interception & evaporation from wet surfaces

2. Overland flow into streams: quickflow

4. Uptake by plants for transpiration (+ soil evaporation)

14

2

3

Step 4 – Plant uptake and transpitation

(Epot – IntercEff * Einterc) * W_avail

1.0

0

Soil water content

FC*DroughtFactor(VegType)

PWPEnergy driven,

e.g.Penman

Evaporation of intercepted water reduces transp.

demand

3. Subsurface flow into streams: ‘interflow’ or ‘soilquickflow’

1. Interception & evaporation from wet surfaces

5. Gradual release to streams through deep soil pathways

2. Overland flow into streams: quickflow

4. Uptake by plants for trans-piration (+ soil evaporation)

14

2

3

5

Step 5 – Percolation to streams as ‘slow flow’

SaturationPercolation Fraction

GW release Fraction Baseflow

GW store

RootZone store

3. Subsurface flow into streams: ‘interflow’ or ‘soilquickflow’

1. Interception & evaporation from wet surfaces

5. Gradual release to streams through deep soil pathways

2. Overland flow into streams: quickflow

4. Uptake by plants for transpiration (+ soil evaporation)

14

2

3

5

Unit hydrograph – what happens to an ‘average’ drop of rainfall?

Topology of stream network: distances to array of observation points

Obs point 1 2 3 4 5

SubA 15 -1 -1 7 .

SubB 16 -1 -1 8 .

SubC 14 8 2 -1 .

SubD 8 1 -1 -1 .

…..

F

G

D

C

E

BA

1

2

3 4

Inherentinterception &

water useproperties

Rai

nfal

l per

day

pe

r su

bcat

chm

ent

Potentially: surface infiltration properties per landcover type as a function of time (LU change per subcatchment)

Subcatchments

Tim

e

Inherent properties: - soil and groundwater storage capacity, - soil drainage & GW release fraction- routing time from stream to river monitoring point

Array dimensions in the model

Model implementation in Excel

GenRiver.xls :

1. Rain & Debit data (daily)

2. Land cover

3. Subcatchment info

Model implementation in Stella

GenRiver.stm

Model sector

Model implementation in Stella

GenRiver.stm

GenRiver.stm Input section

Model implementation in Stella

GenRiver.stm

GenRiver.stm Patch level water

balance

Model implementation in Stella

GenRiver.stm

GenRiver.stm River flow

Default run of GenRiver 1.0measured predicted

measured predicted

When seen over a long time series, both under- and over-estimates occur in dry periods, but the model tends to exaggerate

peaks

The model is in the ‘right range’ but underestimates flows in dry periods and exaggerates peaks

measured predicted

Model implementation in Stella

GenRiver.stm

GenRiver.stm Output sector

GenRiver application in Sumberjaya - Indonesia

Using 2 time series of land cover fractions :

Year 3(%) Year 20(%)

Forest 58 14

Cropland 22 11

Coffee 12 70

Explore the effect of land cover &

spatial pattern for rainfall on river flow

Cumulative water balance

River flow using Pathcy & Homogenous rain

Patchy year 3 Patchy year 20

Hm year 3 Hm year 20

SpatRain.xls

SpatRain.exe

WShedInd.xlsGenRiver.stm

What we offer

Input dataOutput -

hydrographs

Criteria & indicators of watershed functions

Participants Expectations?

Climate, soil, scale, land use

0

5

10

15

20

25

30

0 50 100 150Rainfall (3 stations), mm day-1

Riv

er f

low

, mm

day

-11975-1981

1982-1988

1990-1998

y = 0.02x + 0.85

y = -0.19x + 0.53

R2 = 0.01

0.10.2

0.30.4

0.50.6

0.70.8

0.91.0

0.35 0.45 0.55 0.65 0.75 0.85

Total Water Yield Fraction

Ind

ica

tors

y = -0.33x + 0.99

R2 = 0.46

y = 0.02x + 0.65

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.35 0.45 0.55 0.65 0.75 0.85Total Water Yield Fraction

Ind

ica

tors

Relative buffering

Buffering

Buffering Peak Events

Lowest Monthly Flow

Simulation results: current ‘MixedLU’ situation not much different from ‘forest’, but for a ‘Degraded soil’

buffering would be much lessHomogenous Rain

0

5

10

15

20

25

0 20 40 60 80 100Rain exeedance, mm day -1

Riv

erf

low

ex

ee

da

nc

e,

mm

da

y -

1

AllForest MixedLU AllGrass MixedLU(Act)

Patchy Rain

0

5

10

15

20

25

0 20 40 60 80 100Rain exeedance, mm day -1

Riv

erfl

ow

exe

edan

ce,

mm

day

-1

AllForest MixedLU AllGrass MixedLU(Act)

Homogenous rain Patchy rain

currentDegraded soil

currentDegraded soil