Teknologi Konservasi_Danau

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PRELIMINARY DEVELOPMENT

OF VERTICAL SEGMENTATIONMODEL FOR WATER QUALITY

PREDICTION IN ELONGATED

RESERVOIRS

Priana SudjonoDept. of Environmental Engineering

Bandung Institute of Technology

[email protected]

1



Review on reservoir

Water quantity of reservoir

Water quality of reservoir

Mathematical development Application and discussion

Conclusion

Content

2



Jatiluhur reservoir, West Java 3



Saguling reservoir, West Java4



5



Introduction

Reservoir usually support cities

Industries

Recreation

Transportation

Fisheries

Aesthetics

Also: Irrigated Agriculture

Flood Control

Power Plant

WATER QUANTITY OF RESERVOIR

6



7



Morphology of Reservoirs

The form of a Reservoir determines the

characteristic of:Physical processes

Chemistry of water

Biological diversity

Steep sided that usually deep. Such as V shaped

basins: biologically unproductive

Shallow depressions: greather contact between

water and Sediment: Biologically productive

(natural lakes)

Reservoir in Java, such as Saguling, Jatiluhur are

shallow at the entrance and deep at the outlet zone

8



Morphometric Parameter

Max open water length

Surface area

Storage volume

Mean depth (Vol/area)

Length of shore line

Shoreline development

shore line development, dimensionless

length of shore linbe, kmsurface area, km2

9



Many natural Lakes are subcircular or eleptical

Elongated reservoirs in river valley

Water renewal time of a Reservoir

Q is coming from river inflow, groundwater

seepage.

Outflow is the outflow and evaporation

2 < < 3 ≈ 5 =

Vol

q

10



11



Thermal Stratification

12



Solar radiation penetrates to reservoirs

Solar energy = f (latitude; season of the year)

Light is absorbed by water = f(wave length)

Long wavelength (red) dissipates within impounded

of pure water Short wavelength (blue) - penetrate deeper

So there will be stratification

13



14



Uniform stratification

15



16



Surface Water Movement

Mixing

17



Internal Movement of Water

……………. …………….

…………….

…..…………….

………………….

……….

…………….

…………….

…..

….. …..

…..…..

…..

reservoir

reservoir

reservoir

river

river

river

nutrient

Density factor

Density factor

18



19



W ATER QUALITY IN RESERVOIR

Problem

Dam or reservoir is usually long and narrow

following the regime of rivers

In shallow area light penetrate to the bottomThe productivity is not uniform

20



Mayor consideration in WQM:

Water quality control

Beneficial use Dilution of wastewater

Water quality control

We need to predict water quality

21



22



23



Oxygen Content

O2 from Atmosphere Photosynthesis

Inorganic CarbonInorganic forms: CO2, HCO3

-, CO3=

pH=4,3

H2CO3 H+ +HCO3- H+ + CO3

=

pH=4,5 pH=8,3

Bicarbonate ion Carbonate ion

24



Inorganic carbon

Seepage of groundwater

Surface drainage

Respiration of aquatic animals

Bacteriological

decomposition

of organic matter

25



Blue green algae fixation N2

Organic N

26



Input Nutrient in Eutrophic Reservoir

Surface water rich in nutrientsDrainage from cultivated farmlands

Cattle feedlots from inorg fertilizer and Manure

Municipal wastewaters

Fish cages

27



The Nitrogen Cycle in a Reservoir

28



29



The Phosphorous Cycle in a Reservoir

30



Ecology of Lakes and Reservoirs

31



Aquatic Community

Trophogenic: planktonic and animals

Algae photosynthesisfood

Tropholyctic: decomposition and low DO 32



• Chlorophyl a

• Planktonic algae

• Phytoplankton• Zooplankton

• Blue green Algae

Plant life in most enriched lakes is dominated byBlue Green Algae

Phytoplankton = f (Temp, Light, Mixing, Species

Competition, Predator, Nutrient)

Algae = f (Nutrient (P))

33



Cultural Eutrophication

Natural Environments Eutrophication isslow

Cultural Eutrophication is accelerated by

fertilization of a reservoir, stream arising from

pollution associated with

Population Growth

Industrial Development

Intensive Agriculture

34



The response of aquatic ecosystems to increased

input of Nutrients is greater productivity to the

detrimental of Water Quality

Decaying blue-

green algae

Excessive growth

of phytoplanktonreducing

transparancy

Increasedorganic content depleting DO

• release foul and odor

• loss of less tolerant fish

species• littoral zones choked

with aquatic weeds

Cultural eutrophication short period of a few

years after introduction of excess Nutrient.35



Allowable Nutrient Loadings

Data on the indicator parameters of nutrient

concentrations:

can’t be applieddirectly in Engg.

Analysis

36



However, by relating

Trophic level nutrient loading

from external and

cycling within a

Reservoir

Eutrophication

can be described by

Mathematical models

37



Vollenweider (1970)

Correlated “Data on annual phosporus Loadings”

“Mean Lake Depth” “Degree of Enrichment”

Permissible loading is The maximum allowable load

for a reservoir to remain oligotrophic indefinitely

38



typical plant tissue of phytoplankton and

Macrophytes contains phosphorus, nitrogen, and

carbon in the approximate ratio of 1P: 7N : 40C per100 dry weight).

The Phosphorus Loadings include all biologically

available forms of which the majority are dissolved

orthophosphate and acid hydrolyzable phosphate.

The principle inorganic nitrogen forms taken up by

plants are Nitrate and Ammonia.

influene the

degree ofEutrophication

39



Not equal to

Dillon (1974):

Some Lakes had very high Loadings with corresponding

Low chlorophyl a concentrations, high transparancy, andsmall oxygen deficits during the summer.

This discrepancy was attributed to the high rates of water

flowing through these lakes as a result of large watershed

areas relative to lake volumes

40



MATHEMATICAL DEVELOPMENT

Water Quantity Model

Water Quality Model

41



Surface Heat and Mass Exchange

Energetic of surface layer

Vertical diffusion in the hypolimnion

Inflow dynamicsOutflow dynamics

Dyresm (dynamic reservoir simulation model)

42



Difficulties in building models applicable for

Indonesian situation

1. Lack of data

2. Ecological cycle or process takes place all over

the year (the weather is warm)

3. Less fund needed

43

T i l R i E t hi ti M d l (TREM)



The schematization: reservoir is divided into (m) segments that the

water in the segment remain for a time-step

then moves to the direction of flow to the next segment. The number

of segment is estimated by dividing hydraulic detention time by

)( t ∆

)( t ∆

1 m

overland flowsubsurface flow

intake

evaporation

main

stream

intake

evaporation

outlet

overland flowsubsurface flow

Tropical Reservoir Eutrophication Model (TREM)

44



The incoming water to the first segment consists ofwater from the main river and side inlet such

as small rivers or subsurface flow and overland

flow, . During a time-step, the volume of the

river water to the first segment is and the

volume of side inlet is . Then the volume of the

first segment is

Water Quantity Model

where

45



In every segment: agriculture, water supply,

evaporation or other activities need water, as their

total amount of water intake is .

During a time-step, the volume of intake-water,

as;

So that, the volume of water in the first segment,

t t t t VoVsVr V 111 −+=

t t t VoViV 111 −=

t qoVo t

n

t

n ∆∗=

46



It is assumed that all water in upper segment

moves to the downstream segment, and side inflow

and intake also take place, then the general

equation can be written as

t

n

t

n

t

n VsV Vi += −

−

1

1

if Then,

t

n

t

n

t

n VoViV −=

Initial volume is placed as for all segmentsinit V

47



At the last segment where overflow weir is placed

as in the figure, the flow depends on the dead

storage that is the volume of the last segmentunder the weir.

Vd V t

m

⟩if overflow takes place as much as Vd V t

m −

if

if

Vd V t

m ⟨ overflow does not occur, then the

volume of water in the segment ist

mV

Vd V t

m = overflow does not occur

48



Load of pollutants in reservoir comes from river

water, overland flow, and activities in segments,

such as fish farming. Pollutant load at the first

segment during a specified time

Water Quality Model

( )t ∆

t t t t l Li Lr L 111 −+= where

t t t ciQr Lr =1

t t t t f coqs Li 1111 +=

49



While at other segments :

t

n

t

n

t

n

t

n l Li L L −+=

−

−

1

1

It is assumed that water intake contents pollutant at

average concentration. The amount of pollutant taken

out from the segment ist

t t

n C qol =

It is assumed that water in a segment is completely

mixed, so the average concentration:

t

n

t

nt

n

V

LC =

50



During a time-step the pollutant may involve in

physical and biochemical processes that alter the

concentration.

For example, the alteration can be predicted by

using first order of reaction as:

t k t

n

t

n eC C ∆−−

−=

1

1

t

nC = concentration at segment )(n at time )(t k = coefficient reaction rate for the pollutant.

In case conservative pollutants are concerned,

reaction rate does not take place but massbalance principle can be applied.

51



The computer model is applied into Saguling

reservoir that is divided into 12 segments

APPLICATION OF THE MODEL

52



Water Quantity

0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

1 2 3 4 5 6 7 8 9 10 11 12

Segment

V o l

u m e ( m 3 )

The volume of reservoir in all segments at day 252 in 1991.

53



0.0E+00

5.0E+07

1.0E+08

1.5E+08

2.0E+08

14 56 98 140 182 224 266 308 350

Julian day, 1991

V o l u m e ( m 3 )

The volume of water in segment 11th.

54



No River flow

Pollutant

concentration in the

main river water

Fish

farming

1*

Qr ci exists

2 Qr ci none

3 Qr ci33.0 none

4 Qr ci33.0 exists

*) actual condition

. Scenario of altering pollutants in the management.

Water Quality

55



0

0.2

0.4

0.6

0.8

1

1 2 3 4 5 6 7 8 9 10 11 12

Segment

P h

o s p h o r ( g / m 3 )

Calculated

Measured

Concentration of pollutant along the reservoir at day 252

year 1991 and the calculated results using data of actual

condition (scenario 1). 56



0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300 350 400

Julian day, 1991

P h

o s p h o r ( g / m 3 )

Fluctuation of concentration of pollutant at segment

eleven using data of actual condition in 1991 (scenario 1).57



0

0.2

0.4

0.6

0.8

1

0 1 2 3 4 5 6 7 8 9 10 11 12

Segment

P H o s p h o r ( g / m 3 )

Concentration of pollutant along the reservoir atday 252 in 1991 given scenario 3.

58



0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300 350 400

Julian day, 1991

P

h o s p h o r ( g / m 3

)

Fluctuation of concentration of pollutant at

segment eleven given scenario 3.59



CONCLUSION

Water quality of in a reservoir is under the

influence of point sources and diffuse sources

quality of Main River water

overland flow, andactivities in segments.

The fate of pollutant in a reservoir depends on the

water movement characteristics and biochemicalprocesses that are specific for each segment.

60



The reservoir is divided into segments

activities related to pollutant increments and water

consumption could be included in a mathematical

model.

Water in a segment is assumed to move to the nextsegment and at the same time alterations on

pollutant concentrations take place.

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