A methodology for groundwater management in dolomitic terrains with the Schoonspruit compartment as pilot area

Abstract

English: The thesis proposed to use the principle of prior conceptual model explanation (PCME) by LeGrand & Rosen, 2000, as base to develop a technical methodology towards groundwater management in dolomitic terrains, with the development of a groundwater management tool. The Schoonspruit Dolomitic Compartment was used as case study to evaluate the aquifer with current information, test the developed methodology on and develop a technical groundwater management tool. A phased approach was adopted with a geohydrological assessment of the study area as phase 1 and the development of a technical methodology and the development of the groundwater management tool as phase 2. The aim of the geohydrological assessment was the use of the PCME approach, basic geohydrological principles and previous studies to evaluate the current status of the aquifer. This was done with a description of current information and an evaluation of new information and data. The Schoonspruit Dolomitic Compartment is a dolomitic aquifer situated to the North and Northwest of the town Ventersdorp in the Northwest Province, South Africa. The compartment has been named after the Schoonspruit Eye, which is dependent on the compartment for flow. The Schoonspruit Eye, in turn, is the sole reason why the Schoonspruit has a constant flow and provides a municipality and two surface water irrigation boards with surface water all year round. Several water users abstract groundwater from the compartment impacting on the flow of the Schoonspruit Eye. With the proclamation of The National Water Act, Act 36 of 1998, groundwater was seen as a resource that needed management and, although very little information existed in most cases, Regional Offices of the DW AF, had to start taking decisions, based on sound scientific principles, as to allocable volwnes from the groundwater resources. The Schoonspruit dolomitic regime were defined, aquifer characteristics determined, groundwater quality quantified and recharge/rainfall relationships of groundwater levels and spring flow determined with the saturated volume fluctuation (SVF), moving average (MA) and cumulative rainfall departure (CRD) methods. Two zones were identified as groundwater management units in the compartment and groundwater balances for the two zones defined. The spring flow simulation equation was determined for use in all simulations related to the drainage area of the Schoonspruit Eye. The aim of the technical methodology was to provide a technical framework, which could easily be extrapolated and applied to other dolomitic areas. The methodology distinguished between essential and supplementary information needed for groundwater management in dolomitic areas. A flowchart was developed, as blueprint, when assessing dolomitic areas for the purpose of groundwater management, an overview given with regard to the legal and institutional principles that should be applied in such areas, a detailed description given with regard to the geotechnical controls that govern the groundwater flow and characteristics in dolomitic areas and the basic principles governing the development of a groundwater management tool outlined, with input and output parameters defined. The aim of the groundwater management tool was to provide a first order technical tool, which is practical and workable, for use by the Water User Association in determining allocable volumes. Input and output parameters used were proven to be sufficient for defming quantity and quality issues in the Schoonspruit Dolomitic Compartment. Allocable volumes can be determined for the 2 zones and the Schoonspruit Eye flow simulated, with the MA method, using predicative rainfall data and the drinking water quality classes were introduced, as part of an early warning system, where drinking water quality is of concern.

Afrikaans: Die thesis gebruik die beginsels van prior conceptual model explanation (PCME) van Legrand & Rosen, 2000, as basis om 'n tegniese metodologie te ontwikkel rakende grondwater bestuur in dolomitiese omgewings, asook die ontwikkeling van 'n grondwater bestuurstoestel. Die Schoonspruit Dolomitiese Kompartement was gebruik as gevalle studie om die akwifeer te evalueer met bestaande inligting, die metodologie op te toets en die tegniese grondwater bestuurstoestel te ontwikkel. Die thesis is in fases gedoen met die geohidrologiese ondersoek as fase 1 en die ontwikkeling van die tegniese metodologie en bestuurstoestel as fase 2. Die doel van die geohidrologiese ondersoek was om die PCME benadering, basiese geohidrologiese beginsels en vorige studies te gebruik in 'n evaluasie van die huidige toestand van die akwifeer. Dit is bereik deur 'n beslaywing van bestaande inligting en die evaluasie van nuwe inligting en data. Die Schoonspruit Dolomitiese Kompartement is 'n dolomitiese akwifeer wat Noord en Noordwes van die dorp Ventersdorp gelee is in die Noordwes Provinsie, Suid-Arika. Die kompartement is vernoem na die Schoonspruit Oog, wat afhanklik is van die kompartement vir oppervlak water vloei. Die Schoonspruit Oog is ook die rede hoekom die Schoonspruit 'n konstante vloei het en 'n munisipaliteit en twee oppervlak water besproemgsskemas oppervlak water regdeur die jaar het. Verskeie water gebruikers onttrek grondwater uit die kompartement en impakteer sodoende op die vloei van die Schoonspruit Oog. Met die proklamasies van die Nasional Waterwet, Wet 36 van 1998, is grondwater erken as 'n bron wat bestuur moes word en, alhoewel min inligting omtrent sekere areas bestaan het, moes Streeks Kantore van die DWAF begin besluite neem rakende beskikbare volumes vanaf grondwater bronne, gebaseer op wetenskaplike feite. Die Schoonspruit dolornitiese omgewing is gedefinieer, akwifeer kenmerke bepaal, grondwater kwaliteit gekwantifiseer en aanvulling/reenval verhoudings van grondwater vlakke en fontein vloeie bepaal, met die versadigde volume fluktuasie (SVF), bewegende gemiddelde (MA) en kumulatiewe reenval afwyking (CRD) metodes. Twee sones is identifiseer as grondwater bestuurseenhede in die kompartement en grondwater balanse vir beide is bepaal. Die fontein simulasie vergelyking is bepaal, vir gebruik in alle simulasies wat met die dreinerings area van die Schoonspruit Oog te doen het. Die doel van die tegniese metodologie was om 'n tegniese raamwerk te verskaf, wat maklik ekstrapoleer en toegepas kan word op ander dolomitiese areas. Die metodologie onderskei tussen noodsaaklike en opsionele inligting wat benodig word vir grondwater bestuur in dolomiete. 'n Vloeidiagram is ontwikkel as konsepmodel wanneer dolomitiese areas ondersoek word vir grondwater bestuurs doeleindes, 'n oorsig is gegee rakende wetlike en institusionele beginsels wat toegepas moet word, 'n gedetailleerde beskrywing is gegee van geotegniese kontroles wat grondwater vloei in sulke areas beheer en die kenmerke van dolomitiese areas en die basiese beginsels van die grondwater bestuurs toestel is verduidelik, met die invoer en produk parameters gedefinieer. Die doel van die grondwater bestuurstoestel was om 'n eerste orde tegniese toestel te voorsien, wat prakties en werkbaar is, vir gebruik deur die Water Gebruikers Vereniging, vir die bepaling van beskikbare volumes vir water toekennings. Daar is bewys dat invoer en produk parameters voldoende is om die probleme rondom kwaliteit en kwantiteit in die kompartement te definieer. Beskikbare volumes in die twee sones kan bepaal word en die Schoonspruit Oog fontein vloei simuleer word, met die MA metode, deur gebruik te maak van voorspelde reenval data. Die drinkwater kwaliteit klasse is in ag geneern, as deel van 'n vroee waarskuwings stelsel, in areas waar drinkwater kwaliteit van belang is.