Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for “source water supply and protection” strategies

Emelko, M. B., et al., 2011. Water Research

Original research (primary data)
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Abstract

Forests form the critical source water areas for downstream drinking water supplies in many parts of the world, including the Rocky Mountain regions of North America. Large scale natural disturbances from wildfire and severe insect infestation are more likely because of warming climate and can significantly impact water quality downstream of forested headwaters regions. To investigate potential implications of changing climate and wildfire on drinking water treatment, the 2003 Lost Creek Wildfire in Alberta, Canada was studied. Four years of comprehensive hydrology and water quality data from seven watersheds were evaluated and synthesized to assess the implications of wildfire and post-fire intervention (salvage-logging) on downstream drinking water treatment. The 95th percentile turbidity and DOC remained low in streams draining unburned watersheds (5.1 NTU, 3.8 mg/L), even during periods of potential treatment challenge (e.g., stormflows, spring freshet); in contrast, they were elevated in streams draining burned (15.3 NTU, 4.6 mg/L) and salvage-logged (18.8 NTU, 9.9 mg/L) watersheds. Persistent increases in these parameters and observed increases in other contaminants such as nutrients, heavy metals, and chlorophyll-a in discharge from burned and salvage-logged watersheds present important economic and operational challenges for water treatment; most notably, a potential increased dependence on solids and DOC removal processes. Many traditional source water protection strategies would fail to adequately identify and evaluate many of the significant wildfire- and post-fire management-associated implications to drinking water “treatability”; accordingly, it is proposed that “source water supply and protection strategies” should be developed to consider a suppliers’ ability to provide adequate quantities of potable water to meet demand by addressing all aspects of drinking water “supply” (i.e., quantity, timing of availability, and quality) and their relationship to “treatability” in response to land disturbance.

Case studies

Basic information

  • Case ID: INT-153-1
  • Intervention type: Management
  • Intervention description:

    Salvage logging. No description of the practice given by the study but salvage logging literally means salvaging the logs from burned forests. Here a large fire burned more than 21 000 ha and research stations were established to sample water quality in unburned watersheds, burned watersheds, and burned + salvage logged watersheds.

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Reduced water quality  Negative Water quality measures – pH, Dissolved organic carbon, stream turbidity, dissolved organic nitrogen, total phosphorus, microbial community analysis, optimal polyaluminum chloride doses needed to treat water, mercury Proportion of time during study period that reference catchment source water exceeded a turbidity threshold (10 NTU)
  • Approach implemented in the field: Yes
  • Specific location:

    Lyons creek east and west catchments in the upper Oldman River Basin, southern Alberta

  • Country: Canada
  • Habitat/Biome type: Montane/Alpine |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: The study attempts to study the impact of salvage logging post fires on water quality generated by forested headwaters in western north america. The study compares water quality from unburned watersheds, burned watersheds, and burned watersheds + salvage logging. Salvage logging is not implemented as a practice to promote water quality, it is merely a measure to salvage wood for timber production. We are interested in capturing the effects of this water management intervention on water quality, and the comparator is therefore the burned watersheds with no salvage logging. “The 95th percentile turbidity and DOC remained low in streams draining unburned watersheds (5.1 NTU, 3.8 mg/L), even during periods of potential treatment challenge (e.g., stormflows, spring freshet); in contrast, they were elevated in streams draining burned (15.3 NTU, 4.6 mg/L) and salvage-logged (18.8 NTU, 9.9 mg/L) watersheds.” “higher levels of DON were measured in discharge from the post-fire salvage-logged catchments, relative to burned and unburned catchments, even four years post-fire” Phosphorus concentrations and mercury contamination were similar in burned and burned + salvage logged watersheds. “Turbidity/TSS, DOC, TP, DON, Hg, chlorophyll-a, and Actinobacteria-like microbial concentrations were all higher in streams draining burned and salvage-logged watersheds than in those draining reference watersheds…TP, DOC, and chlorophyll-a remained elevated in the discharge from burned and salvage-logged catchments four years after the wildfire”
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures: N/A
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures: N/A
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: Yes
  • Experimental evalution done: In-situ/field
  • Non-experimental evalution done: Not applicable
  • Study is systematic: