Ground water Management

In the previous article we have looked at the pump test stage of drilling a borehole, and for many this seem to be the final stage of groundwater development. However, to complete the picture and take cognizance of the fact that groundwater is a resource that needs to be managed, we have to now look at the different phases as a summary, as well as considering the information and strategies that will assist in managing this resource effectively.

The activities described in the previous articles can now be summarized for groundwater development. The development of groundwater resources generally takes place in three phases namely exploration, evaluation and finally the exploitation or management phase.

During the exploration phase, surface and subsurface geological and geophysical techniques are applied to assist in finding suitable aquifers. During the evaluation phase, boreholes are drilled, constructed, developed and tested to establish Hydrogeological parameters and calculate possible borehole, aquifer and basin (or catchment) yields. The final (and ongoing) phase in groundwater development is the exploitation or management phase. This is the stage whereby groundwater monitoring and aquifer performances are monitored and fine tuned to assist in the consideration of the optimum development strategies as well as the interactions between groundwater abstraction and the hydrological cycle. In all the areas where groundwater is either the sole source of water, or where groundwater is used to augment water supply, the management of this resource will become increasingly important. The pressure on this resource worldwide will increase as the demand for increased production and from increased populations will require more utilization of this scarce resource.

Borehole information

Every borehole owner will benefit from keeping the following information on his/her borehole: Geological description of samples as encountered during drilling; borehole specifications e.g. borehole diameter drilled, final depth, length and type of casing installed, and static water level after drilling. Additional information for the borehole includes the blow yield as measured during drilling and the test pump information. The details to be kept on the borehole pump include the type of pump installed, the pump depth as well as the date of initial installation.

To furthermore ensure a continuous supply of water from a borehole additional information should be measured on a regular basis. This information should be kept in a data basis and could be represented in graphical manner for ease of understanding. This include the water level measurement on a weekly or monthly basis (depending on the pumping schedule as well as the importance of the borehole), rainfall on a daily weekly or monthly basis, and finally the volume of water pumped on a weekly or monthly basis, or alternatively the time the borehole was pumped.

Borehole management

A borehole water user can now, based on this information start to manage this resource by adhering to some basic groundwater management principles. To become an effective businessman or farmer sound financial control and planning is essential. Similarly if a person depends on groundwater for a large percentage of his income, proper management of this valuable resource is of utmost importance. By analyzing the data recorded on a regular basis, by means of graphical presentation or modeling**, one can have an early warning system setup. Steady declines in borehole water levels, even approaching the pump inlet, will provide a clear indication of over pumping of the borehole. Based on this up to date information one can immediately implement remedial action by either reducing the pump rate or the pumping periods.

Modeling

Modeling refers to the simulation of borehole, aquifer and basin groundwater responses by means of a computer generated mathematical model. There are number computer codes developed specially for the simulation of groundwater flow and abstraction patterns as well as the movement and remediation of groundwater pollution. Modeling is an important tool used in combining all available hydrological, hydrogeological and geological information to assist in the planning of exploration, development, exploitation and management of a groundwater resource.

As noted from the above discussion, groundwater management should take place on various levels, starting from the localized borehole owner and user to the regional aquifer, basin and catchment area. Ultimately groundwater development will rely heavily on management principles applied by Local authorities, Government and Inter Governmental development planning and management strategies. In this regard the South African Water Law has been developed with specific outcomes and responsibilities in mind. Next week we look at the South African Water Law and how it affect the local borehole owner and user as well as the role that is envisaged for Local Authorities and Government.