“No water, no life. No blue, no green.”

Sylvia Earle

The Breede River is about 257 km long and has a catchment area of about 12 625km². Runoff from the catchment is highly seasonal with high flows and floods in winter and low floes in summer. With the creation of all the dams in the catchment, the mean annual runoff has been reduced by approximately 42 percent from the reference conditions to present state.

Fresh water brings in cold oxygenated water bring down nutrients from the catchment. Besides having managerial impacts, fresh water is needed for certain species niche needs. Certain species require differing fresh water levels for some part of their life cycles. High saline levels may cause die back of fresh water species and usually affect the species that can tolerate certain saline levels but only for a certain amount of time such as reed banks.

Fresh water inflow is also necessary for flushing of the estuary. Sediment brought down from the catchment deposits along its course and excess sediment is usually pushed out of the mouth. The fresh water flow needs to be strong enough to counteract the oceans sediment input to push this sediment out of the mouth. A lack of fresh water flow could result in the shallowing of the estuary and the creation of sandbanks.

Water quantity is the most important factor determining the classification of an estuary (we are at present classified as a Category B estuary). This available fresh water is sought after by most landowners on the river from source to the mouth and an understanding of water use and availability is of huge importance in preventing damage to the system.

Fresh water flow is monitored by the Department of Water Affairs and is made available to the LBRCT. The LBRCT collects this data weekly and stores it in a database for analyses.

 

Episodic events

Episodic events in this context refer to droughts and floods. These are normal events that occur that have dramatic effects on the estuary. Flooding will flush the system and is highly necessary. Floods also have a major effect on the developments along the estuary and therefore floods have managerial impacts. Droughts are more difficult to monitor, but also have effects on the system usually creating a highly saline system that will affect saline intolerant species especially further upstream. Most of the management implications are reactive, with flooding one will have disaster management and with droughts it may be necessary to request the release of fresh water from dams upstream.

The LBRCT makes sure they collect as much information in times of these episodic events as possible. Having long term data on these events will allow us to identify trends that may be used in the future to avoid the level of damage these events may cause.

Water Quality in this context refers to the presence and concentration of minerals, toxins and microbes. Some of the indices would have a negative impact on the estuary such as chemicals. In the area of the estuary there is a large farming community and the risk of agrochemical pollution is high. There are no major industries along the Breede, but sewerage systems are rife and pose another threat to the system. Other indices like minerals are needed in the system but extremely high or low levels of these trace elements could have negative effects on the system and its species.

Water quality monitoring is highly specialised and the lab testing very expensive and does not make sense for the LBRCT in its lack of experience to do their own water quality monitoring. The Department of Water Affairs is testing these indices and has agreed to allow the LBRCT access to the results. The station used is Bree at Swellendam (H7H006) as it the station closest to the mouth. Localised pollution issues need to be handled reactively and reported to the correct authorities to be handled. The Swellendam Municipality also tests the estuarine waters seasonally in terms of human health so total coliforms and faecal coliforms as well as some pathogens. There is also quite a lot of monitoring done high up river, but all this information is available to the LBRCT.

The LBRCT once again collects this data and stores it on its database. This data is then available for analyses.

 

Salinity distribution

Salinity distribution is physically done by the LBRCT. This distribution is another measure of the amount of fresh water entering the system. The runs are done on the spring high every month and readings are taken every 2km and for every metre of water depth. These readings are repeated until the reading reads fresh water. Therefore one can tell where the fresh water begins. If fresh water makes its way down to the mouth, the fresh water inflow is high. These results also have management implications.

Other indices collected in these runs are dissolved oxygen, temperature, pH and conductivity. All these indices can be used to pick up trends in order to understand the relative health of the system.