Conference for Wetlands: Monitoring, Modelling and Management

22 – 25 September 2005, Wierzba

Modelling Water Balances of Wetlands with

controlled Drainage and Sub-irrigation Systems

O. Dietrich1, M. Redetzky2 & K. Schwärzel3

1 Leibniz-Centre for Agricultural Landscape Research (ZALF) e.V., Institute of Landscape Hydrology

2 WASY Institute for Water Resources Planning and System Research Ltd.

3 Technische Universität Dresden, Institute of Soil Science

Wetlands in North-Eastern GermanyWetlands in Elbe-Lowland:

• ~ 20 % of area• drained for agricultural

land use• low precipitation• sub-irrigation systems

Study site Spreewald

Berlin

Investigation Region Spreewald

Size:• Biosphere Reserve 475 km²• Lowland Area 320 km²

Water Management System:• approx.1600 km Streams and

Ditches• approx.600 Weirs• Basin (2.500 km²) with open pit

mining (problems)

Climatic Characteristics (1961/90):• Precipitation 530 mm/a• Air Temperature 9 °C• pot. Evapotranspiration 610 mm/a

Land Use und Water Management System of the Spreewald Wetland

Land UseForestFieldGrasslandIntensive GrasslandWaterUrbanUnused

Water Balance of Wetlands

Imperm

eable

Aquifer

Basin

Infiltration

Infiltr

ation

Fen with drainage and sub-irrigation system E

P E

Gi

Si

SoGo

∆S

∆S = P – E + Si + Gi – So - Go

Water Management in Wetlands

Stre

am 2

Stre

am 1

Ditc

h

Dra

inag

eInlet Weir

Outlet (Pumping Station)

• Drainage and sub-irriga-tion for agricultural land use

• Surplus water from basins, often with reservoirs

• Regulation of ditch and ground water levels by weirs

Requirements for the Water Balance Modelling

Model requirements

Application of a model combination of WBalMo® + WABI

Special site conditions of drained/sub-irrigated wetlands

Water balance for groundwater influenced areas

Heterogeneous soils and land use

Heterogeneous terrain with varying ground water levels below surface

Water management in the wetland

Control of ground water levels in the sub-areas by subirrigation systems

Connection of wetland + basin

Surplus water from sub-basins with water management

Basic ModellsWABIWBalMo®

WABI sub-area = water user in WBalMo

Simulation sub-area

Running waters with balance profile

Reservoir

Water user

• River basins represent by simulation sub-areas, running waters, balance profiles, water users, reservoirs

• Stochastic generated input values (P, ETP, discharge) – Monte-Carlo-Simulation

• Deterministic reproduction of water utilisation processes

• Time step one month• Statistical analysis of registered events• Possibility to introduce other models in a

WBalMo model

• Simple water balance model for ground water influenced areas with drainage/sub-irrigation systems (rewetting investigations of fen sites)

• Grid-based• Investigation site is divided in sub-areas• Assumption: horizontal ground water level in

every sub area• Time step one month• Target water levels and inflows in the sub-areas

are pretended

WaterSaturated Zone

Ground water below surface

Inundation

Unsaturated ZoneSection A-A

Weir system

Main streamStreamDitch

Small weirLarge weirPumping stationSub-area

Stream system System structureSub-areas WABI-user

WBalMo Spreewald – System structure

Main streamStream

WBalMo Spreewald –System Structure

WABI-user (sub-area)Main streamStream

WBalMo Spreewald

Module WABI within WBalMo

Module Wetland Water Balance (WABI)

Etam,j,g,k GWTar,i,k

hNN,i,j Si

Wetland Data

Index: g – Ground Water Class below Surface, g = 1...7i – Sub-area, i = 1...197j – HRU, j = 1...27k – Month, k = 1...12n – Realisation, n = 1...10

WBa

lMo

WB

alM

o

Pk,n

Etpm,k,Etpk,nC

limat

ic D

ata

Bas

in D

isch

arge RBor,k,n

Rin,k,n

ModulREGINF

RWwd,i,k,n SEnd,i,k,n

GWEnd,i,k,nRDef,i,k,n Rout,i,k,n

GWStart,i,k+1,n 1

Rout,k,n

Etaj,g,k,n Ai,j,g,k,n

Etai,k,n

CWBi,k,n

GWStart,i,kwith k = 1

SStart,i,kwith k = 1

STar,i,k

SCWB,i,k,n RDem,i,k,n

1

Validation - Water Balance of the Wetland in total (So – (Si + Gi + P))

Calibration - Period 1990/94

-25-20-15-10

-505

10Jan Feb Mrz Apr May Jun Jul Aug Sep Oct Nov Dec

m³/s

obs calcValidation - Period 1995/99

-25-20-15-10-505

10Jan Feb Mrz Apr May Jun Jul Aug Sep Oct Nov Dec

m³/s

obs calc

R2 = 0,66

-25

�

Æ÷

ÆÚ

�

K

K

-25 ‰�w O�w ��w � æ 5

obs in m³/s

calc

in m

³/s

R2 = 0,71

-25

�

Ë\

Ëã

�

P

P

-25 Š�~ Q�~ ��~ ë 5

obs in m³/sca

lc in

m³/s

Validation - Ground Water Level

-1.6

-1.2

-0.8

-0.4

0

0.4

0.8

Mea

n G

roun

dwat

er L

evel

in m

LSW

, obs

LSW

, cal

cU

SW

, obs

US

W, c

alc

LSW

-Bor

der A

rea,

obs

LSW

-Bor

der A

rea,

cal

cU

SW

-Nor

th, o

bsU

SW

-Nor

th, c

alc

US

W-S

outh

, obs

US

W-S

outh

, cal

c

Section of Spreewald Wetland

QuantileMin/Max0.05/0.950.10/0.900.25/0.750.50

Validation - Period 1995/99

-1.6

-1.2

-0.8

-0.4

0

0.4

0.8

Mea

n G

roun

dwat

er L

evel

in m

LSW

, obs

LSW

, cal

cU

SW, o

bsU

SW

, cal

cLS

W-B

orde

r Are

a, o

bsLS

W-B

orde

r Are

a, c

alc

US

W-N

orth

, obs

USW

-Nor

th, c

alc

USW

-Sou

th, o

bsU

SW

-Sou

th, c

alc

Section of Spreewald Wetland

QuantileMin/Max0.10/0.900.05/0.950.25/0.750.50

Calibration - Period 1990/94

Range and quantiles of observed and calculated ground water levels in different parts of the Spreewald Wetland

LSW – Lower SpreewaldUSW – Upper Spreewald

Water Management Options

Main rivers and streams for water supply and drainage in the Spreewald Wetland

Changes in water management between status quo and redistribution scenario

Nordumfluter

Nor

dum

flute

r

Spree

Großes FließMittelkanalBurg-Lübbener Kanal

Mal

xeS

pree

Status quo Scenario

Nordumfluter

Nor

dum

flute

r

Spree

Großes FließMittelkanal

Burg-Lübbener Kanal

Mal

xeS

pree

!!

Redistribution Scenario

Effects of Water ManagementStatus quo Scenario

Comparison of the July ground levels of status quo scenario 2048/52 (50. percentile) with the levels of the status quo scenario 2003/07

Redistribution Scenario

Comparison of the July ground levels of the redistribution scenario 2048/52 (50. percentile) with the the status quo scenario 2048/52

Summary

• Water balance of many wetlands is influenced by water resources management systems in wetlands and basins

• Integration of water resources management in water balance modelling for planning of development (restoration, WFD, global change) of wetlands is necessary

• Combination of the models WBalMo and WABI shows one example

• Results show, how the possibilities of water resources management can be used for aims of wetland protection

Thank You