Long-term trends of changes in the quality of water discharging from abandoned coal mines have been studied for 32 long-established discharges in the Midland Valley of Scotland. Six discharges have been studied in greater detail, providing insights into discharge quality evolution over more than a century. It has been found that minewater pollution is most severe in the first few decades after a discharge begins (the 'first flush'), and that even the largest systems settle down to a lower level of pollution (particularly in terms of iron concentration) within 40 years. Long-term iron concentrations of less than 30 mg/1 are typical, and many are less than 10 mg/1. Low pH values (which might justify the over-used term 'acid mine drainage') do not generally persist, due to the rapid buffering of localized acidic waters by carbonates (both natural carbonates, and those introduced as rock powder for fire precautions during mining). This is corroborated by alkalinity concentrations, which tend to be highest in the early years of a discharge. While the pyrite content of the worked sequence strongly influences initial water quality (in terms of pH, iron and sulphate) during the 'first flush', there appears to be no correlation between long-term iron concentrations of discharges and pyrite content of local strata. Rather, higher levels are found in any sequence where there is scope for fluctuations of the water table in worked ground near to the discharge. A scientific approach to minewater remediation should allow for active treatment of discharges for the first decade or two, followed by long-term passive treatment after asymptotic pollutant concentrations are attained.

Seven household treatment technologies for the removal of arsenic (Alcan, BUET, DPHE/DANIDA, Garnet, Sono, Stevens, Tetrahedron) were each evaluated using water from 63 different tube wells taken from 3 different regions of Bangladesh. The technologies that were evaluated were chosen from those that appeared user friendly, readily available and whose promoters were open to participate in the study. Arsenic concentrations in feed and treated waters were analysed by the PeCo 75 arsenic field test kit, AA-hydride generation and ICP-AES. Feed water arsenic concentrations were found to be up to 600 microg l(-1). The more advanced treatment methods using: activated alumina (Alcan, BUET); metallic iron (Sono); anionic exchange resin (Tetrahedron) and iron coagulation (Stevens) were found to be most easily used and efficiently reduced arsenic concentrations to below the Bangladesh drinking water standard (0.05 mg As l(-1)). The use of aluminium sulphate coagulants and permanganate oxidants in the DPHE/DANIDA technology introduced unacceptably high concentrations of aluminium and manganese into the treated waters and are not recommended in household water treatment applications. While arseric concentrations were initially considered to be of paramount importance, it became clear that such technologies can increase the risk of bacterial contamination in the treated water and this needs serious consideration as this could create a hazard much greater than the arsenic contained in the water. Ground waters sampled during the course of this study were mostly found to be bacteria free. To minimize any risks relating to bacterial contamination the addition of hypochlorite or the boiling of water is necessary.

Groundwater provides a range of services to people in Southern Africa; however, the benefits provided by these services are often not fully appreciated and factored into decisions about groundwater management and use. After outlining briefly the importance of groundwater in the region and the pressures facing groundwater, this paper discusses how economic valuation can help improve its management. The main focus of the paper is the presentation of the practical 5-step economic valuation methodology that has been developed as part of the Southern African Development Community (SADC) Groundwater and Drought Management Project. This methodology can be generally applied to groundwater management issues across the SADC region. The methodology is based upon an ecosystem services approach which considers all the potential services that groundwater provides, which can result in improvements in human welfare. These services include provisioning services such as water for domestic use, agriculture and industry; regulating services such as the recharge of surface waters and carbon storage benefits; and cultural services such as the tourism associated with wildlife at groundwater-fed watering holes. The methodology incorporates a 2-tiered valuation approach. The Tier 1 valuation is based on market pricing and value-transfer approaches and can provide an initial view of the economic value of a resource in a particular use. A value-transfer tool has been developed, which allows the user to select from a menu of the currently available transfer values for use in an assessment. A Tier 2 valuation requires more detailed primary studies and may be required following a Tier 1 assessment where more certainty in decision-making is required. The methodology has been tested at 4 pilot sites in the region. An example of the application of the SADC groundwater-valuation methodology in Namibia is presented in this paper. The paper concludes with recommendations for the development of groundwater valuation in the region. Emphasis is placed on training, the commissioning of more groundwater-valuation studies and the need for more scientific research to facilitate the valuation of groundwater-regulating services.

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