Thesis (MEng)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The Berg River is one of the largest rivers in the winter rainfall area of the Western Cape and is one of
the most important water supply sources of the area. The Riviersonderend-Berg system needs to be
expanded in order to meet increasing water demands of the Greater Cape Town (GCT) region. The
implementation of future schemes will remove additional fresh water from the Berg River main stem,
which will give rise to increased nutrient levels and higher salinity in the water. A water quality
information system (WQIS) has been proposed to benefit the management of water resources, the flow
quantity and the quality of the water. A part of this WQIS will be a water-quality simulation model that
characterizes the water quality situation and is able to predict water quality responses to future
implementations, as well as simulate different scenarios that can be used for management purposes.
The objective of this study is to represent the water quality situation of the Berg River in a simulation
model by implementing, testing and verifying a water quality simulation model, and assembling a
hydraulic and water quality database suitable to meet foregoing objectives.
This study firstly examined the water quality variables of concern: pH, Total Dissolved Salts (TDS) and
phosphates to develop an understanding of the water quality responses and causes of the main stem of
the Berg River system.
A thorough review of the available models has been undertaken in the light of certain selection criteria,
before determining that DUFLOW would be an acceptable model for this study. The water quality
variables that have been modelled are TDS, Phosphates as P04, Oxygen and Temperature. As no
predefined module simulating temperature, TDS and COD was included; these algorithms, describing
the processes of these water quality variables have been additionally coded. The coding was possible,
as DUFLOW' s water quality module consists of an open structure. The predefined water quality module
was simplified to only include the water quality process algorithms, for water quality variables where
data was available. Unfortunately, phosphates were mainly simulated on advection, and the influence
of all the additional processes could not be assessed.
All data gathering and preparation for the model had to be completed before commencing the model configuration. This included information on cross-sections, historical flow records, bridges and weirs
for the hydraulic component ofDUFLOW. For the water quality module, information on historical grab
samples has been obtained and 'infilled' to provide daily time series.
To simulate the water quality in a river as accurately as possible, the flow simulation needs to be
accurate. Ungauged subcatchment runoff was added to the simulation model to improve the
correspondence between the simulated and the measured flow. Calibration of the water quality part of
DUFLOW was completed by adjusting the different parameters after a sensitivity analysis. The model
was verified by using a different time period than for the configuration, to ensure that an independent
data set has been used.
After configuring, calibrating and verifying the model, the applicability of the model could be tested for
different scenario runs. Three scenarios were chosen according to real situations:
• a short term effluent spill, with and without water releases from an upstream source (either
Skuifraam Dam or Voëlvlei Dam);
• the impact on the flow and water quality situation of the river when an upstream dam is built;
• a long term management control scenario, that analyses load or concentration releases into the
river according to limitations upstream and downstream of the discharge location.
The scenario analysis provides an opportunity to assess the applicability of DUFLOW to simulate real
time management and operational issues in a river and to aid in management decisions. / AFRIKAANSE OPSOMMING: Die Bergrivier is een van die grootste riviere in die winterreënvalgebied van die Weskaap en is een van
die mees belangrike waterverskaffingsbronne in die area. Die Riviersonderend-Bergrivier-stelsel moet
uitgebrei word om aan die groeiende waterbehoefte van die groter Kaapse Metropolitaanse Area te
voldoen. Die implementering van toekomstige skemas sal addisionele vars water uit die hoof-loop van
die Bergrivier onttrek, wat tot hoër voedingstof-vlakke en soutgehalte in die water sal lei. 'n
Waterkwaliteitsinformasiestelsel (WQIS) sal van nut wees om die vloei-omvang en waterkwaliteit van
waterbronne te bestuur. 'n Deel van die WQIS sal 'n waterkwaliteit-simulasiemodel wees, wat die
waterkwaliteitsituasie sal kan ontleed, waterkwaliteit-reaksies op toekomstige implementerings kan
voorspel, asook verskeie scenarios vir bestuursdoeleindes kan simuleer.
Hierdie studie behandel spesifiek die waterkwaliteitsveranderlikes pH, totale opgeloste soute, fosfate,
temperatuur en suurstof om 'n begrip te ontwikkel van die waterkwaliteitsreaksies en oorsake van die
hoofloop van die Bergriviersisteem. Die doelwit van hierdie studie is om die waterkwaliteitsituasie van
die Bergrivier uit te beeld deur die implementering, toets en kalibrasie van 'n waterkwaliteit-simulasie
model, asook die insameling van hidrouliese- en waterkwaliteitsdata om aan bogenoemde doelwitte te
voldoen.
'n Reeks beskikbare modelle is deeglik ondersoek voordat besluit is dat die DUFLOW model 'n gepaste
model vir hierdie spesifieke studie is. Die keuse was gebaseer op spesifieke vereistes wat as belangrik
beskou is deur potensiële bestuursgeorienteerde gebruiksgroepe. Die waterkwaliteitsveranderlikes wat
gemodelleer is, is totale opgeloste soute, fosfate as P04, suurstof en temperatuur. Omdat geen
voorgegewe temperatuur-, TDS- en COD modules in die model ingesluit is nie, is die algoritmes wat
die prosesse van hierdie waterkwaliteitsveranderlikes beskryf, addisioneel gekodeer. Die kodering is
moontlik gemaak deur die oop struktuur van DUFLOW se waterkwaliteitsmodule. Die voorgegewe
waterkwaliteitsmodule is vereenvoudig om alleenlik die waterkwaliteit proses-algoritmes in ag te neem
wanneer data vir waterkwaliteitsveranderlikes beskikbaar was. Ongelukkig is die fosfate hoofsaaklik op
beweging gesimuleer, en die invloed van alle addisionele prosesse kon nie getoets word nie.
Alle data-insameling en -voorbereidings vir die model moes voltooi word, voordat begin kon word met
die opstel van die simulasie-model. Dit het inligting oor dwarssnitte, historiese vloeirekords, brik en keerwalle vir die hidrouliese komponent van DUFLOW ingesluit. Vir die waterkwaliteitsmodule is
inligting van historiese bemonstering verkry en ingevulom 'n daaglikse tydreeks te verkry.
Om die water-kwaliteit van 'n rivier so akkuraat as moontlik te simuleer, moet die vloei-simulasie
redelik akkuraat wees. Ongemete sub-opvanggebied afloop is bygetel om die korrelasie tussen die
gesimuleerde en gemete vloei te verbeter. Kalibrasie van die waterkwaliteitmodule van DUFLOW is
voltooi deur die verskillende parameters te verstel na 'n sensitiwiteits-analise. Die model is geverifieer
deur 'n ander tydperiode as die vir die opstel te gebruik, om sodoende te verseker dat Inonafhanklike data
stel gebruik word.
Na die opstel, kalibrasie en verifiering van die model, kon dit toegepass word vir verskillende bestuursscenanos.
Drie scenarios is na aanleiding van werklike situasies gekies:
'n korttermyn uitvloeisel storting-situasie met en sonder loslatings van 'n stroomop bron (Of
Skuifraamdam Of Voëlvleidam),
die impak op die vloei- en waterkwaliteitsituasie van die rivier sou 'n dam stroomop gebou word.
'n langtermyn bestuurs-scenario waarin die lading en konsentrasies, veroorsaak deur die
loslatings vanuit die dam na die rivier, ontleed word na aanleiding van beperkings stroomop en
-af van die loslatingsplek.
Die analise van die scenarios verskaf 'n geleentheid om die toepaslikheid van DUFLOW te ondersoek
om werklike operasionele aangeleenthede te simuleer en om sodoende bestuursbesluite te vergemaklik.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51624 |
| Date | 12 1900 |
| Creators | Nitsche, N. C. |
| Contributors | Gorgens, A. H. M., Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 1 v. (various pagings) : ill. |
| Rights | Stellenbosch University |
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