The purpose of the study is to understand quantitatively the spatial distribution of groundwater recharge in the Sana'a Basin, Yemen i.e. irrigation recharge, wadi recharge and urban recharge and to assess the impact of these components on the groundwater quality. A combination of field measurements and modelling was used to determine the irrigation return for several crops and soil types. Over the basin, the total return flows, between 20 to 40 % of the water applied, are about 30 MCM/year. A method was developed to calculate recharge through ephemeral wadi beds using an indirect approach, requiring only daily rainfall data and geomorphological observations. The technique combines a rainfall-runoff model with calculation of daily water balance for the wadi channel. The method was applied to two wadis with sufficient subsurface data to estimate groundwater recharge independently from calibration of groundwater models for the shallow aquifer. The values of infiltration calculated by groundwater flow model were in good agreement with the results of the channel water balance model. Regression analysis was used to derive a generalised relationship between recharge and wadi flows. Application of this technique allows extension of wadi recharge estimates to numerous ungauged wadis over 20 years. Wadi recharge over the Sana'a basin is erratic and varies between 129 MCM and 3 MCM with an average of 38 MCM/year. An inventory of abstraction by private wells in Sana'a city, has allowed an improved estimation of urban recharge over the last 20 years, an average of 60% of the water abstracted (76% supplied). Water chemistry indicates that the shallow aquifer within the plain and lower reaches of major wadis has been polluted. However, dilution is taking place through mixing with the deep fresh water through the boreholes. Total annual recharge varies between 143 MCM and 21 MCM with an average of 66 MCM. This represents a significant amount of the annual average abstraction of 82 MCM. Previous estimate of recharge to aquifers of the basin has been less soundly based.

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The thesis presents a sociological analysis of international food standard-setting in the Codex Alimentarius Commission (the Codex). The Codex is an intergovernmental organisation jointly administered by the UN Food and Agricultural Organisation and the World Health Organisation. The main activity of member governments who participate in the Codex is the negotiation of international food standards, which are referenced by W orId Trade Organisation agreements. Although international food standards are significant instruments which structure the agri-food system, little social science research has been conducted on the process by which such standards are set. In order to develop an in-depth analysis of the science-based standard-setting process, the thesis analyses a case-study of the attempt to agree a definition of dietary fibre within the Codex. Agreeing a definition of dietary fibre was a protracted and contentious process within the Codex, with important implications for food product development and the creation of new markets. Methods used in the study included: observations of meetings, document analysis and thirty-two interviews with scientists, government delegates and food industry and consumer representatives. In this case-study, the concept of epistemic communities - defined by Haas (1992a: 3) as " ... a network of professionals with recognised expertise and competence in a particular domain and an authoritative claim to policy-relevant knowledge within the domain or issue-area" - was deemed to provide a weak explanation for the standard-setting process due to a failure to address the conditions giving rise to particular knowledge claims. Instead - and following critiques developed within the sociology of science and technology - the analysis suggests that international food standard-setting uses scientific knowledge claims, but cannot be said to be wholly based upon science because of the constitutive entanglement of science and politics. The thesis argues that the production of a definition for dietary fibre followed a methodology of standard-setting that required dietary fibre to became a 'boundary object' (Star and Griesemer, 1989) - an identifiable object around which conflicting groups can co-operate because the object possesses just enough ambiguity to allow for multiple interpretations. The thesis concludes that, in this case-study, on-going scientific controversy does not prevent the agreement of a food standard - despite food standards being 'science-based' - if the standard in question can be negotiated as a boundary object. The thesis provides novel social scientific insights into a little studied, but increasingly significant, area of the agri-food system.