Botn

Historie

Botn is an inland fjord in the municipality of Rissa in Sør-Trøndelag county, Norway. It flows through a short, small river into the Sundsbukta, a small bay off the Trondheimsfjord. The village of Årnset lies on the north shore of Botn.Hydrography and water qualityThe extraordinarily shallow, narrow, and long inlet restrains the water exchange severely. The daily tidal amplitude is in the order of centimetres, about 1/10 of the tidal amplitude of the supplying Trondheimsfjord. The shallow river connecting Botn to the Trondheimsfjord blocks out more than half of the tidal wave, making the moon-phase driven tidal flood height cycles the primal driving force for the internal water level, with an abnormally small neap flood effect (zero has been observed during lowest neap tides and meteorologically suppressed sea level).In addition, the inlet is connected to a secluded bay sheltered from the strong tidal currents in the main fjord. This leads to accumulation and recycling of the exported surface brackish water, heavily reducing the sea water portion of imported water that can sink in and refresh the deeper waters, thus giving a natural stratification with stagnant (uninhabitable) water below a depth of 7to, and a poisonous rotten bottom water beneath. As another unusual anomaly, this hydrographic blocking of seawater seems to persist in calm periods even in the winter, denying import of the usual winterly bottom water renewal that otherwise is normal in fjords, and leading to a decrease in Botn's deep water oxygen levels during winter.