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BERG RIVER MONITORING PROGRAMME

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Announcements

Surveys


Chemical and Physical Characteristics of the Water Resource


River water quality monitoring
Estuarine sediment transport monitoring and hydraulic modelling
Estuarine salinity modelling and monitoring

River water quality monitoring
The ongoing monitoring programme being carried out at existing DWAF sampling sites on the Berg River and on selected tributaries of the Berg, will be updated at the start of this study, such that water quality data specified in the Terms of Reference for this study are collected from the relevant sites.

Continuous temperature recorders will be installed at two sites on the Berg River - a control site (Site 1), upstream of upper reaches of the planned Skuifraam dam (only a probe need be installed at this site, since continuous measurement devices are already in place at the upstream weir site (Franz Muski, DWAF, Western Cape), and a downstream site (Site 2), between the dam outlet and the confluence with the Franschhoek tributary. Temperature measurements collected immediately upstream of the Franschhoek tributary during quarterly sampling, would allow a rough estimate of downstream recovery between Site 2 and the Franschhoek tributary.

Fieldwork and collection of water quality samples will be carried out by a trainee assistant, working under the supervision of Dr Day. The assistant will ideally be a student who is already involved in studies in water quality or river health aspects. This proposal undertakes to ensure that a previous disadvantaged individual is employed in this role - suitable candidates will be drawn from University of the Western Cape and University of Cape Town. The assistant will be trained initially in site selection and water quality sampling protocol, and thereafter will take responsibility for the collection of water quality data for the river, working in conjunction with the macroinvertebrate specialist.

Data collection:
DWAF water chemistry records will be augmented by other important measurements of system variables collected at the five sites for which biological monitoring will be undertaken.
These measurements will comprise:
· water temperature, pH, conductivity, dissolved oxygen - all measured in situ
· turbidity, nitrate and nitrite nitrogen, ammonia nitrogen, Kjeldahl nitrogen, total phosphorus and ortho-phosphorus - analysed from collected water samples
· Monitoring of the composition of aquatic algae to provide qualitative data on the density and diversity of species assemblages, from samples collected from specified biotopes, and the significance of these data, in terms of water quality, as well as in terms of ecosystem function, will form part of the baseline report.
· Monitoring of algal abundance (periphyton and chlorophyll-a)
· Analysis of samples for Escherichia coli and sampling of cyanobacteria from selected sites along the river has been added to the sampling programme, as recommended during the IFR study, to provide human health data
· Analysis of phosphorus concentrations in sediments from the middle and lower reaches of the Berg River, to provide pre-construction data for use in the modelling of sediment loading recommended for these reaches
In addition, ad hoc sampling of river water and analysis for the presence of cyanobacteria will be conducted in the Berg River at Sites 1 and 2, and Sites 4 and 5, to monitor the effect of releases of water from Theewaterskloof and Voelvlei, respectively, when these dams have blooms of toxic cyanobacteria. Sites 1 and 4 would function as upstream control sites for each dam.

Monitoring frequency:
· Monitoring of DWAF water quality sampling sites will continue at present sampling frequencies, and at DWAF cost, with registration of additional water quality variables at selected sites
· Continuous temperature recorders will be installed at selected sites; data will be collected by DWAF and made available to the consultants
· All other water quality variables listed above will be collected from monitoring sites on a quarterly basis, at the same time as the invertebrate sampling, and analysed as follows:
Ø water temperature, pH, conductivity, dissolved oxygen - all measured in situ
Ø total suspended solids, nitrate and nitrite nitrogen, ammonia nitrogen, Kjeldahl nitrogen, total phosphorus and ortho-phosphorus - from samples collected during quarterly sampling trips and analysed at IWQS in Pretoria (at DWAF's cost). It is suggested that analysis could also take place at the DWAF-approved SABS laboratory in Cape Town, thus reducing costs of transport to IWQS and potential errors and accidents en route.
Ø Escherichia coli bacteria and chlorophyll-a will be analysed at the CSIR laboratories in Stellenbosch, due to the short time that can elapse between sample collection and analysis (SABS laboratories do not analyse for chlorophyll-a)
· Ad hoc sampling of Sites 1,2 and 4, 5 for the presence of cyanobacteria will be carried out when the consultants are informed by DWAF that toxic cyanobacteria blooms are evident in Theewaterskloof Dam (during times of release) and Voelvlei Dam. Three assessments / year / dam have been allowed for in the provisional budget for this section.

Deliverables:
· Initialisation report - synthesis of existing information regarding ecosystem structure and function.
· Annual reports including details of sampling programme, compilation of data collected and brief interpretation of the significance of observed changes.
· Input into final baseline monitoring report

Estuarine sediment transport monitoring and hydraulic modelling
Monitoring of the estuary will be undertaken to define baseline characteristics in estuary geometry and sediments. However, for meaningful comparisons to be drawn in the future, a conceptual model of hydraulic linkages is considered to be an essential component of the baseline monitoring programme, as outlined in section 3.2.1 of this document. This will require accurate survey of the channel along the length of the estuary, as well as the development of a digital terrain model for the floodplain.

Survey data for the compilation of the hydraulic / sediment transport model will be collected from 40 cross-sections, spaced at intervals up the 50km length of the estuary. The optimum locations for the cross-section stations will be identified jointly by the sediment and water quality modellers. It is likely that these will be spaced closer together near to the mouth where salinity gradients are likely to be strongest (see below) and greatest variation in sediment structure can be expected. Surveys will be conducted using a Trimble Single frequency GPS (absolute accuracy height (20 mm) linked to a survey quality 300 MHz Ulvertec echo sounder (accuracy rating 20 mm +2PP1000) by navlog Software, each transect extending from above the high water mark on one bank to the same position on the opposite bank and is to cover a width of 20 m. These surveys will tie in with the digital terrain model.

The digital terrain model (DTM) and ortho-imagery for the Berg River Estuary and surrounding flood plain area will be produced at a 1:10 000 scale, with ground pixel size 0.25 m and RMS 0.167 m. Aerial photography required for the DTM will be undertaken in February-March 2003.

Data collection:
Following completion of the digital terrain model and initial surveying, the hydraulic model (see section 4.5.2) will be set up and calibrated based on tidal and flood data, taking into account the effects of channel network and floodplains, vegetation, cohesive sediment, water losses and wind. The model will describe flood attenuation and hydraulics of the floodplain. The following data will be collected to compile the model:
· Bed sediment sampling: grab and cores, and grading analysis
· Investigate sources of sediment
· Investigate historical aerial photos and planform changes
· Spring tide monitoring with water level recording, as well as inflow and outflow to the estuary
· Flood monitoring (one): water levels, inflow and outflow

Monitoring frequency:
· once-off sampling for each task, in 2003

Deliverables:
· Model and report, to inform the Estuarine modelling workshop and to be included in the Initialisation report.

Estuarine salinity modelling and monitoring
This component of the monitoring programme will involve measuring temperature salinity, oxygen and pH at selected depths on each of the surveyed cross-sections along the length of the estuary. The period of measurement for each sampling event has been expanded over the original DWAF TORs to a measurement period extending over at least one spring-neap cycle, involving sections at high and low, spring and neap tides. Temperature/salinity recorders will be deployed during each measuring period at intervals up the estuary channel, and current measurements be made at one section near the mouth of the estuary at spring and neap tides as this will assist in determining stratification patterns and the magnitude of the tidal prism in the estuary. Concurrent weather data will be obtained from Cape Town International airport or the airforce base at Saldanha, corresponding with the monitoring periods.

Ideally when studying the salinity profile of an estuary, one should cover the whole distance from the mouth to the top of the estuary simultaneously, but in practice the hour or so of slack water at high and low tides is satisfactory. It is important to realise that the tide progresses upstream, which means that the slack water also propagates upstream, and one can thus move with it making measurements. Peak tide reaches Kersefontein (46 km from the river mouth) about 4 hours after it reaches the mouth, so that approximately 5 hrs can be spent on one section.

The above information, in conjunction with data derived from a hydraulic flow model of the estuary, will be used to develop or enhance the calibration and verification of an existing numerical water quality model for the estuary.

Data collection:
During each sampling period the following activities will be undertaken (using a conductivity/temperature/depth meter with measurements taken at 0.25 m intervals at the same cross sections as for the sediment sampling):
· At spring high tide (or low, depending on convenience) a complete section from the mouth to about 50 km will be surveyed as described above.
· Next day, at spring low tide (or high, depending on convenience) a second complete section from the mouth to about 50 km will be surveyed.
· One week later, at neap high tide (or low) a third complete section from the mouth to about 50 km will be surveyed.
· Next day, at neap low tide (or high) a fourth complete section from the mouth to about 50 km will be surveyed.

Monitoring frequency:
· Quarterly, for the duration of the monitoring programme

Deliverables:
· Initialisation report - synthesis of existing information regarding ecosystem structure and function.
· Annual reports including details of sampling programme, compilation of data collected and brief interpretation of the significance of observed changes.
· Input into final baseline monitoring report