Will UK peatland restoration reduce dissolved organic matter concentrations in upland drinking water supplies?

Abstract

Abstract. Rising dissolved organic matter (DOM) concentrations, and associated increases in water colour, have posed a potential problem for the UK water industry since the phenomenon was first reported in the early 1990s. Elevated DOM concentrations in raw water are of particular concern in upland catchments dominated by organic soils where DOM production tends to be highest. In recent years, water companies have considered the capacity for catchment interventions to improve raw water quality at source, relieving the need for costly and complex engineering solutions in treatment works, but there is considerable uncertainty around the effectiveness of these measures. One of the primary evidence gaps is the extent to which catchment management is capable of influencing DOM concentrations at the point of abstraction, field studies rarely extending beyond sub-catchment or stream scale. Our review of the published evidence suggests that catchment management could make a contribution to mitigating recent DOM increases in some circumstances, particularly where plantation forestry has been grown on peat, and where control of nutrients in runoff could reduce in-reservoir DOM production. Evidence for the efficacy of most other measures that target reductions in DOM loading for catchment to reservoir remains insufficient to support wider scale application. Collectively, these measures have the potential to reduce DOM concentrations in drinking water reservoirs but they must be selected on a site-specific basis, where the scale, effect size and duration of the catchment intervention are considered in relation to both the treatment capacity of the works and future projected DOM trends.

Climate change and drinking water from Scottish peatlands: Where increasing DOC is an issue?

“…On the other hand, other restoration activities have, in the short term, led to an increase of DOC (Qassim et al, 2015) or produced no difference (Alderson et al, 2019). A comprehensive review can be found in Williamson et al (2020), who conclude that restoration can increase the resilience of the system, bringing positive effects to the water sector, but alone it is not enough. Tools to monitor and predict the future DOC, are needed to make each intervention (whether it deals with the management of the catchment or it is an infrastructural operation) more targeted and well-timed.…”