The study investigates the physical, rheological and sedimentation parameters of two characteristic mud samples taken from the reservoir Sulejów in the area of the intake of drinking water for the town of Łódź. Rheological research was conducted using a rotational viscometer Rheotest 2, Couette-Searle type. The limit volumetric concentrations of the two muds were found to be 1.4 and 1.8%, respectively. Using the relationships established by Migniot, the volumetric concentrations corresponding with the transition from easy erosion to hard erosion were calculated. Sedimentation studies provided a basis for estimating the characteristic times of mud settlement. Finally, the average critical flow velocities, enabling the erosion of the top layer of mud to begin, were determined and were found to be 1.16 and 1.37 m · s-1, respectively. As the mean discharge of the water intake is 2 m3 · s-1, the water flow to the intake has the average velocity of 0.0154 m3 · s-1, which value is about 80 times smaller than the mean velocity causing mud erosion. Therefore, already after 2–3 days of settling, the cohesive mud deposited in the water intake area will not be eroded by the water stream flowing to the intake.

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