The promoters of the large groundwater developments implemented in the 1970's paid little attention to the effects of pumping on soil moisture. A field study, conducted in 1979 in the Tern Area of the Shropshire Groundwater Scheme, revealed that significant quantities of the available moisture could be removed from the root zone of vegetation when drawdown of shallow watertables occurred. Arguments to this effect, supported by the field study evidence, were successfully presented at the Shropshire Groundwater Scheme public inquiry. The aim of this study has been to expand the work which was undertaken in connection with the Shropshire Groundwater Scheme, and to develop a method whereby the effects of groundwater pumping on vegetation can be assessed, and hence the impacts minimised. Two concepts, the critical height and the soil sensitivity depth, formulated during the initial work are at the core of the Environmental Impact Assessment method whose development is described. A programme of laboratory experiments on soil columns is described, as is the derivation of relationships for determining critical heights and field capacity moisture profiles. These relationships are subsequently employed in evaluating the effects of groundwater drawdown. In employing the environmental assessment technique, digitised maps of relevant features of the Tern Area are combined to produce composite maps delineating the extent of the areas which are potentially sensitive to groundwater drawdown. A series of crop yield/moisture loss functions are then employed to estimate the impact of simulated pumping events on the agricultural community of the Tern Area. Finally, guidelines, based on experience gained through evaluation of the Tern Area case study, are presented for use in the design of soil moisture monitoring systems and in the siting of boreholes. In addition recommendations are made for development of the EIA technique, and further research needs are identified.

Water resource management operations have significantly modified river flow regimes globally, prompting widespread lotic ecosystem responses. There is a growing need to better understand how increasingly prevalent hydrological alterations to riverine systems will affect biota dependent on specific elements of river flow regimes. This thesis examines macroinvertebrate community responses to river flow regimes modified by various water resource management operations across southwest England though four detailed investigations. The first study examines the influence of river impoundments and how macroinvertebrate communities differ between regulated and non-regulated sections of river. Findings from this investigation highlight that flow regulation alters the structure and function of faunal assemblages due to significant changes to the flow regime, rather than stream temperature modifications associated with the reservoirs. The second study focusses on groundwater dominated headwater streams transitioning from temporary (i.e. reaches periodically drying positioned furthest upstream) to perennial flow conditions which are subjected to variable groundwater abstraction intensities. The results indicate that macroinvertebrate communities respond significantly to the duration of antecedent flowing conditions and the spatial proximity of sampling sites to perennial sources; but faunal assemblages are not sensitive to groundwater abstraction. The third study examines how communities inhabiting different organic and mineralogical lotic habitats responded to multiple river flow properties (hydrological indices, anthropogenic flow alteration measures and hydraulic variables) in perennial, groundwater dominated systems. The findings highlight that faunal assemblages are most responsive to local hydraulic conditions measured at the point of sampling, rather than antecedent hydrological conditions. The influence of hydraulic properties on communities differs between lotic habitats, highlighting that mineralogical and organic characteristics of riverbeds strongly mediate how biota respond to flow. The final study presents the results of a long-term (1995-2016), region-wide (spanning Dorset, Hampshire and Wiltshire) examination of macroinvertebrate communities inhabiting groundwater dominated rivers and their responses to hydrological variability (including extreme low- and high-flow events) and anthropogenic flow alterations. The results indicate that indices characterising the proportion of discharge added to (through effluent water returns and low-flow alleviation strategies) or removed from the river (via groundwater abstraction) exert profound effects on faunal assemblages over long-term periods. These results provide empirical evidence that reductions in river discharges via groundwater abstraction of approximately 15% have no perceptible negative ecological effects on macroinvertebrate communities. The results from the four detailed investigations are used to develop conceptual models to illustrate how research undertaken within this thesis can be applied more widely. The findings and study designs presented within this thesis could inform surface and groundwater water resource management operations and underpin the development of environmental flow methodologies required to conserve riverine ecosystems globally.

>Magister Scientiae - MSc / Assessing groundwater-surface water interaction as a decision-making tool licensing water use South Africa: Case study area of Gevonden Farm is the title of the current study with the context that arises from the use of GRAII methodology which uses quaternary catchment boundaries for groundwater abstraction water use licence application assessment during decision making. The problem is that the quaternary catchment scale approach does not provide the scientific bases for site specific scale. The current study argues that such approach provides realistic, practical information at site specific scale and therefore informs the issuing of licences more accurately. The aim of the current study is to improve understanding of how the assessment of groundwater abstraction water use licence should be carried out at a site specific scale to improve decision making during licence issuance. The objective of the study is to outline the scientific study and demonstrate how the investigation that leads to the decision making can be conducted. The study was carried out using hydraulic methods such as pumping test and geochemical analysis method. Hydraulic properties were determined and chemical elements were analysed for and compared with the SANS 241 water quality standards for domestic and agricultural use. Hydraulic properties such as hydraulic conductivity (K), transmissivity (T), yield and storativity (S) were determined. Major and minor ions that are required to be analysed for domestic and agricultural water use were analysed. Piper diagrams and FC method were used to analyse data. The piper diagrams plotted indicated that surface water is mixing with groundwater and that means there is connection between groundwater and surface water. The chemical elements analysed for were compared with SANS 241 water quality standards for domestic and agricultural use. The water quality on the investigated site can be categorized as having good water quality. A sustainable yield estimated from the two boreholes (BH03 and BH05) which was 1.02 Ɩ/s. The available drawdown estimated with reference to the boreholes water strikes that were determined by EC profiling were 135 mbgl from both boreholes. The study recommends the issuance of water use licence with conditions that chemistry of water should be analysed for once a quarter and boreholes water levels should be analysed for once a month.

Groundwater abstraction for irrigation use has steadily increased over the past decades, resulting in additional evaporation to the atmosphere, and increased precipitation. The precipitation stemming from groundwater irrigation (or Groundwater-dependent precipitation) has received little attention during recent years and is solely researched by the Eulerian model. This study aims to provide a supplement and improvement of the global fate of groundwater-dependent precipitation with the Lagrangian model outcome. The analysis combines the UTrack model output between 2008 to 2017, a global groundwater irrigation area map, groundwater abstraction from PCR-GLOBWB version 1, and groundwater irrigation efficiency to generate the global groundwater-dependent precipitation trajectory from 2001 to 2010. The primary assumption is that atmospheric factors do not change significantly in all pressure levels during 2001 – 2010 and 2008 – 2017. The simulation result shows that groundwater-dependent precipitation is generally more substantial in Asia than in other continents. Bhutan, Bangladesh, Nepal, India, Yemen, and Afghanistan are the top six countries receiving high groundwater-dependent precipitation contributions monthly and yearly. Moreover, groundwater-dependent precipitation in the continent and country shows a significant seasonal change in the monthly average. A country or continent with a high groundwater abstraction does not necessarily receive a massive amount of groundwater-dependent precipitation regardless of monthly and yearly scale. For instance, China has a yearly average groundwater abstraction of 100 km3 year-1 but receives less than 1% groundwater-dependent precipitation contribution per year. Approximately 75% of groundwater-dependent precipitation falls into the land, and 25% ends in the ocean from 2001 to 2010. The groundwater-dependent precipitation does not significantly contribute to land and ocean, with 0.16% and 0.015%, respectively. Consequently, the study suggests groundwater-dependent precipitation does not have a greater effect on downwind area precipitation on a yearly scale but a larger effect during a specific month. The highest monthly average groundwater-dependent contribution is 18% in January, whereas the highest yearly groundwater-dependent contribution is 2.5% in 2006. Major regions with high groundwater-dependent precipitation contributions are found along the Himalayas Range from January to April and moving eastward to Arabic Peninsula in July.

Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Water resources in South Africa are limited and groundwater plays an important role in supporting basic human needs, sustaining ecosystems and enabling industrial and agricultural development. Sound management practices are necessary to ensure sustainable development of water resources. All groundwater usage must be licensed in compliance with the National Water Act of 1998. A Spatial Decision Support System (SDSS) can be used to assist in the groundwater usage licensing process of the Department of Water Affairs and Forestry (DWAF). The main aim of this study was to develop a SDSS, named Groundwater Abstraction & Licence Evaluation Tool (GALET), that could assist in the process of allocating water use licences and determining the local impact of abstraction, based on existing theory and data. The development was done within ArcView 3.2 using the scripting language Avenue. The Sandveld, an arid stretch of land along the west coast of South Africa that is heavily impacted by groundwater abstraction, was the chosen study area. The data collected for this study included existing borehole, recharge, rainfall and geological information. GALET proved to be capable of calculating essential information needed to evaluate groundwater abstraction, which included drawdown in the water table, zone of influence and the possible effects on features such as rivers and wetlands. Targeted potential users regarded GALET as a useful tool in the process of licensing and groundwater abstraction impact assessment and plans are under way to implement GALET or a derivative thereof at the DWAF regional offices. / AFRIKAANSE OPSOMMING: Waterhulpbronne in Suid-Afrika is beperk en grondwater speel 'n belangrike rol in die ondersteuning van basiese menslike behoeftes, volhouding van ekosisteme asook industriële en landbou-ontwikkeling. Betroubare bestuurspraktyke is noodsaaklik om die volhoubare ontwikkeling van waterhulpbronne te verseker. Alle grondwatergebruik moet volgens die Nasionale Waterwet van 1998 gelisensieer word. 'n Ruimtelike Besluitnemings Ondersteuning Stelsel (RBOS) kan as 'n hulpmiddel gebruik word in die lisensiëringsproses van die Departement van Waterwese en Bosbou. Die hoofdoel van hierdie studie was om 'n RBOS, genoem Groundwater Abstraction & Licence Evaluation Tool (GALET), te ontwikkel wat as hulpmiddel gebruik kan word in die allokeringsproses van watergebruiklisensies en die bepaling van die impak van grondwateronttrekking op die omgewing, gebaseer op bestaande teorie en data. Die ontwikkeling is in ArcView 3.2 met die programmeringstaal Avenue gedoen. Die Sandveld, 'n ariede streek aan die weskus van Suid-Afrika wat onderhewig is aan grootskaalse grondwateronttrekking, is gekies as die studie area. Die data wat vir hierdie studie ingesamel is sluit bestaande boorgat, grondwateraanvulling, reënval en geologiese inligting in. GALET was in staat om belangrike inligting aangaande die evaluering van grondwateronttrekking te bereken, o.a. die daling van die grondwatervlak, die impaksone en die moontlike effekte op landvorms soos riviere en vleilande. Die teikengroep potensiële gebruikers het GALET as 'n nuttige hulpmiddel in die proses van lisensiëring en grondwateronttrekking impakbepaling beskou en planne is onderweg om dit of 'n aangepaste program by die streekskantore van die Departement van Waterwese en Bosbou te implementeer.