Geology of Hampshire's chalk rivers
Chalk rivers in Hampshire are ground fed and rise in the chalk aquifers across the downs.
Chalk river water is crystal clear because rainwater is purified as it percolates through the chalk and emerges as springs in the valley floor. As a result, the water is very alkaline or ‘hard', with a relatively constant temperature due to the water's underground journey through the chalk.
Classic chalk rivers have relatively constant flows throughout the year; rising slightly during the winter as the aquifer is replenished, and gently declining in the summer and autumn.
The need to protect the chalk aquifer from pollution is particularly important as it gives the rivers and their tributaries their distinctive character.
Recently there have been increased concerns about water quality in many of our chalk rivers. It would appear that there are higher levels of phosphate and nitrate in the groundwater causing higher levels of nutrient in the system.
