Small land cover changes in the transboundary Kootenai River basin greatly alter water quality

Abstract

Increased nutrient loading in aquatic environments can have a long-lasting influence on ecosystem processes and functions. The Kootenai River was historically oligotrophic, but nitrate levels have been steadily increasing since the mid-2000s, while phosphorus levels have remained low. Our study objective was to evaluate the current nutrient distribution throughout the Kootenai River watershed in the context of land use and land cover change. Each of the three land cover types we assessed, agriculture, developed areas, and surface mines, encompass less than 1% of the land area in the Kootenai River watershed. We measured nitrate, ammonium, and soluble reactive phosphorus (SRP) monthly at sites spanning 400 river km on the Kootenai River, and co-located tributary sites in British Columbia, Canada, and Montana and Idaho, USA. During July 2017, we measured the same nutrients along each of the selected tributaries with co-located sites at sub-catchment tributaries. Sites were selected to include a range of contributing drainage areas identified as agricultural, developed, or mining. Nutrient concentrations ranged from 0.012 to 4.

Growth of Coal Mining Operations in the Elk River Valley (Canada) Linked to Increasing Solute Transport of Se, NO3–, and SO42– into the Transboundary Koocanusa Reservoir (USA–Canada)

“…KOC is oligotrophic due to low background phosphorus concentrations and limited sediment delivery to the downstream section of the reservoir because of the Libby Dam. Increasing NO 3 – loads from the Elk River coupled with limited phosphorus has the potential to alter food webs through an imbalance of nutrients. − Food web effects from the nutrient imbalance have known ecological consequences downstream of the reservoir in the Kootenai River in MT and Idaho (ID), where phosphorus is now being added to improve food webs for fisheries. , …”

“…30−33 Food web effects from the nutrient imbalance have known ecological consequences downstream of the reservoir in the Kootenai River in MT and Idaho (ID), where phosphorus is now being added to improve food webs for fisheries. 30,34 Se is an essential trace element for life, but excess Se can be toxic to vertebrates and invertebrates. 35 In egg-laying organisms, Se substitutes for sulfur in proteins causing teratogenesis (deformities) in early life stages, among other effects.…”