iMOD Gebruikersdag Deltares | Delft

14 Juni

29 juni 2017

Peter Vermeulen

Frans Roelofsen,

Liduin Burgering

Bennie Minnema

Content

29 juni 2017

UZF SFR MNW

UZF – Onverzadigde zone

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UZF – Unsaturated Zone

The UZF:

• Simulate water flow and storage in the

unsaturated zone and to include precipitation

(RCH-concept); evapotranspiration; EVT-

concept

1. first unsaturated zone;

2. groundwater within EXDP).

• The approach assumes that unsaturated flow

occurs in response to gravity potential

gradients only and ignores negative potential

gradients (upward capillary flow);

• the approach further assumes uniform

hydraulic properties in the unsaturated zone

for each vertical column of model cells*.

• *MF6 support multiply k-horizons

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UZF – Unsaturated Zone

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Method of characteristics:

• velocity of a wave;

• the change in water content of the wave

with time;

• the change in water content with depth

behind the wave, respectively.

1. Wetting front – leading wave

2. Drying – traling wave

3. Waves can overtake others

NSTRAIL = number of trailing wave

increments

NSETS2= number of waves (each

precipitation event generate another wave)

UZF – Unsaturated Zone

Behavior of the unsaturated zone

is given by the Corey Coefficient ɛ,

this determines how permeability

(and thus velocity through the

unsaturated zone) depends on the

moisture content, the higher ɛ the

less recharge is expected from the

unsaturated zone.

Specific Yield (SY) is the

porosity minus the residual

water content

Permeability – and therefore velocity –

and eventually moisture content is

determined by Brooks-Corey function for

unsaturated permeability

UZF – Unsaturated Zone

Grondwater level (red)

Precipitation (blue)

Grondwater Recharge (green)

Output:

• Net recharge;

• Water balance for the unsaturated zone (precipitation, evapotranspiration,

recharge and overland flow*;

• Detailed output: Prints time, ground-water head, and thickness of unsaturated

zone, and cumulative volumes of infiltration, recharge, storage, change in

storage and ground-water discharge to land surface; series of depths and

water contents in the unsaturated zone.

* Not supported in iMOD implementation

UZF – Unsaturated Zone

run 1 2 3 4

CB-

Epsilon

2 2 2 4

EXTWC 0.01 0.10 0.01 0.01

THTI 0.15 0.15 0.01 0.15

Measurement behavior

Extinction Water Content EVT

Initial Water Content

UZF – Tutorial

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SFR – Surface Water Routing

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SFR Overview – Concepts LAYOUT

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𝑄in = 𝑄out

𝑄 = 𝑛𝑤𝑦53𝑆12

𝑦 =𝑄𝑛

𝑤𝑆12

35

• Exchange Groundwater

• Surface overland flow

• Precipitation

• Evaporation

• External sources

Manning’s Equation

w: width of the stream

y: depth of water in the stream

n: Manning’s roughness coefficient

s: slope of stream

SFR Overview – Concepts LIMITATIONS

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No storageterm;

No damping of waves;

Steady state for each timestep (quasi-transient approach);

Uniform flow, driven by gravity and predefined flow directions (per timestep

adjustable though;

Distribution at branching must be specified:

Fixed amount taken from a stream (extraction)

Up to a specified flow rate is diverted to the stream;

Only above a specified flow rate in the stream the flow is diverted;

The diversion rate is assigned by a predefined fraction;

All flow is diverted in excess of a specified flow (flood control).

10.0

11.0

12.0

13.0

14.0

15.0

01

00:00

01

12:00

02

00:00

02

12:00

03

00:00

03

12:00

04

00:00

04

12:00

05

00:00

05

12:00

06

00:00

time

wa

ter

lev

el

[m]

unsteady steady

SFR Overview – Concepts EXCHANGE WITH GROUNDWATER

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Q, q: leakage flux, exchanged amount of water

c: leakage coefficient as ks / d;

w: interface width as function of river stage

L: length of stream

h: head difference between river stage hr and groundwater

level hg

d: sediment layer thickness of river bed

kS: hydraulic conductivity of riverbed

q

q1

q2

Δh

Δh1

Δh2

infiltration

drainage

𝑄 =𝑘𝑠𝑤(ℎ𝑟)𝐿

𝑑Δℎ

𝑐 =𝑘𝑠𝑑

SFR Overview – Concepts COMPUTING WATERLEVELS

1. Interpolation between given levels;

2. Manning‘s Equation with a rectangular cross-section;

3. Manning‘s Equation with a 8-point cross-section;

4. Function assuming stream depth and width can be related to

streamflow by an equation;

5. Table with values of depth and width for given streamflows.

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SFR Implementaton in iMOD DATA STORAGE

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ISG-RIV ISG-SFR

RIV-package SFR-package

BDGRIV BDGSTR

ISG-RIV

Four attributes per calculation

points, many calculation points per

segment allowed – interpolation

over the segments by iMOD

Eleven attributes per calculation

points, only two calculation points

per segment – interpolation over the

segment by the SFR package

Exchange flux between surface-

and groundwater

Exchange flux between surface-

and groundwater

Stream Stages, -Depth, -Width and

-Discharges

SFR Implementaton in iMOD DATA STORAGE

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S1

S2

S3

S4

S5

S6

S8

S7

Transient connections, riverbed width, -conductivity

and -thickness, calculation options, runoff flow

Connection and flow

direction

Cross-sections Discharge-

width/depth relations

SFR Implementaton in iMOD CONNECTIONS

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Functionality

to

interactively

select the

down- or

upstream

connected

stream

diversion

Flow direction

Connection

S1

S2

S3

S4

S5

S6

S8 S7

SFR Implementaton in iMOD GRIDDING FOR SFR PACKAGE

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Intersection with

modelling raster S1

S2

S3

S4

S5

S6

S8 S7

S1

S2

S3

S4

S5

S6

S8 S7

Segment is splitted into 6 reaches

for the model

SFR Implementaton in iMOD RESULTS

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Stream Depths (m)

Stream Discharge (m3/sec)

Transient results:

Stream Depth;

Stream Width;

Stream Stage;

Stream Discharges

per segment written in ISG-file

SFR Implementaton in iMOD RESULTS

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Select more segments, S1,

S2, S6 and S8

S1

S2

S3

S4

S5

S6

S8 S7

Visualize Stream Levels, Stream

Depth, Stream Width or Stream

Discharges over the selected

segment in a profile

S1

S2 S6

S8

SFR Implementaton in iMOD RESULTS

Visualize Stream Levels,

Stream Depth, Stream

Width or Stream Discharges

for a) the selected segments

or b) all segments in the 2D

plot

Select any available date to

display the corresponding

results

.. or rasterize

the results to

conventional

IDF files

SFR Implementaton in iMOD RESULTS

SFR Implemented in IMOD – adapted ISG file – not in RUN file only in

PRJ file

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SFR Tutorial

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MNW – Multi-Node Well

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MNW – Multi-Node Well

The Multi-Node Well package is used to:

• simulate ``long'' wells that are connected to

more than one model layer;

• distribute the abstraction rate vertically

proportional to the transmissivity adjacent to

the well screen;

• when a hydraulic head gradually drops below

the top of a well screen the yield of this

shallow part of the well will also gradually

drop – so: effective extraction can be

different than entered extraction.

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MNW – Multi-Node Well

However:

• differences between the volume of a cell

and the volume of a well-bore;

• differences between the average

hydraulic properties of a cell and those

immediately adjacent to a well

not expected that the computed head for

the node of a finite-difference cell will

accurately reproduce or predict the actual

head or water level in a well at that

location.

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MNW – Multi-Node Well

Head losses:

Solved by computing a hydraulic head in the

cell such that it equals the computed

hydraulic head at the well minus a head

loss term*:

Thiem Equation:

Skin OPTION:

this option allows for formation damage or

skin corrections at the well

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* MNW support more options that are not

supported by the iMOD GUI

MNW – Multi-Node Well

The MNW package can deal with intra

borehole flow and computes a realistic

head loss at the well, this makes the

package mostly applicable for multi-

layered unconfined systems.

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MNW – Implemented in iMOD

29 juni 2017

MNW as IPF-file (with- or without associated TXT-files) in PRJ file not

in RUN file

MNW – Tutorial

29 juni 2017

Contact

29 juni 2017