Groundwater

Introduction

Water located under the ground is called groundwater. The body of rock that holds the water in cracks, fissures and caverns is called an Aquifer. Not all rock types hold water. The aquifer is re-charged from rainfall and water retention, allowing the water to seep into the ground, through the soil and re-fill the aquifer. Change in landuse has a negative impact on the rate of recharge – where open land with high recharge is developed and covered in paving and tar the runoff is directed to stormwater sewers and the recharge rate is decreased. A decreased rate of recharge means that it takes longer for the aquifer to re-fill when it is used. The level of the aquifer is referred to as the water table. The level of the water table changes as the groundwater is used and recharged. Groundwater/aquifers DO NOT follow property boundaries, i.e. one aquifer is shared by many properties.

We can access and use the groundwater for urban (domestic, industrial) and agricultural use*. We access this groundwater either through a well point or a borehole. A well point is a shallow (up to 8metre deep) hole dug into the water table, and the water is either collected by a bucket system or sucked by a surface pump. A borehole is a deeper hole. A borehole can be 15m to over 100m deep. A pump is submerged into the hole and pumps the water to the surface.

Groundwater is a recognized water resource. It is managed and governed by the National Department of Water and Sanitation (DWS) in terms of the NWA 36 of 1998.

Where groundwater is used for domestic purposes, the municipality also has an interest in how the groundwater water is used.

*Depending on how much water and what it is used for, depends on whether a licence from the DWS is required or whether it falls under a General Authorisation (GA). The latest GA for taking groundwater is found here: National-Water-Act-1998-36-1998-Revision-of-General-Authorisation-for-the-taking-20160902-GGN-40243-00538.

Even if the water taken falls within the General Authorisation, the borehole/well point must be registered with the DWS. A schedule 1 use does not require a licence, but if that use is for commercial gain e.g. plant nursery, selling vegetables, then it is no longer a schedule 1 use and will require a section 21 water use licence.

Managing Groundwater

As different parts of the country have different environmental characteristics, i.e. some areas have a high rainfall ad lush vegetation and others areas lower rainfall and more arid vegetation, different parts of the country are characterized differently and the management requirements of water resources differs according to these characteristics, who the water users are, what the impacts to water resources are, etc. In South Africa we follow a catchment approach to water resources management. The runoff across the land flows into different rivers. This runoff or drainage is the catchment of the river. Different catchments and rivers have different characteristics. While groundwater does not adhere to boundaries on the surface of the ground, they are grouped into these catchment areas for management purposes. (Interest reading: South African Quaternary Catchments Database).

There are 19 primary water management (catchment) areas in South Africa, these are managed by 9 Catchment Management Agencies (some are still in the process of being established). These primary catchments cover a very large area. They are further divided into small catchment areas within the primary (1st order) area, called secondary (2nd order) catchments, and broken down further into tertiary (3rd order), quaternary (4th order) and quinary (5th order) catchments. Working in these lower order catchments makes it more practical on the ground to manage the water resources. See a map indicating the catchments across the Western Cape (Source: GEOSS). (The colours in the map indicate the volume of abstraction per quaternary, over a year according to the General Authorisation.)

 

Each quaternary catchment has a number order i.e. A2BC. The “A” refers to the primary catchment, the “2” refers to the secondary catchment within the primary catchment, the BC refers to the next order of catchment. The Greater Cape Town Metropolitan area and surrounding Local Municipal areas fall within the Berg-Olifants Primary Catchment (WMA 9, “G” primary catchment).

The amount of groundwater that can be used in each quaternary catchment has been determined and published by the DWS in the Government Notice. This amount indicates how many litres per day can be taken out of an aquifer per hectare (ha) of land. If the borehole is on a piece of land smaller than a hectare then the volume of water is reduced according the area of the land.  One hectare of land equals a 100m by 100m or 10 000m2.

NOTE: This volume is not based on number of people. If there is 1 person or a 100 people on that ha of land the volume of water remains the same.

The allocations per quaternary catchment can be found here, Appendix B National-Water-Act-1998-36-1998-Revision-of-General-Authorisation-for-the-taking-20160902-GGN-40243-00538 2016.

It is a requirement to meter the amount of groundwater abstracted, whether from a well point or borehole and whatever the water is used for. Metering information must be submitted to the DWS via email: metering@dws.gov.za.

In January 2018 with the severe drought affecting the Western Cape, the DWS placed restrictions on the use of groundwater, limiting the volume of water that can be taken for different uses. This restriction has NOT been lifted. The full Notice can be found here and read in conjunction with the Government Notice 538 above:  government-gazette-ZA-vol-631-no-41381-dated-2018-01-12

Using groundwater is not an endless supply. It is important that the use of groundwater is taken responsibly and within the management rules set out. Over-abstraction, especially with reduced recharge (the below average rainfall also contributes to reduced recharge) is a real threat.