A current meter is a device used to measure the velocity of flowing water. It consists of a propeller or impeller that rotates in proportion to the speed of the water.

A water level recorder is an instrument used to measure and record the water level in a body of water, such as a river, lake, or reservoir.

A turbidimeter is an instrument used to measure the amount of suspended sediment in water. It works by measuring the amount of light that is scattered by the suspended particles.

A rain gauge is an instrument used to measure the amount of rainfall that falls in a given location. It consists of a container that collects the rainwater and a graduated scale that is used to measure the volume of the collected water.

A thermometer is an instrument used to measure the temperature of a substance. It consists of a bulb that contains a liquid, such as mercury or alcohol, that expands or contracts with changes in temperature.

A flowmeter is an instrument used to measure the flow rate of a fluid. It works by measuring the velocity of the flowing fluid and then calculating the flow rate based on the velocity and the cross-sectional area of the pipe or channel.

A hydrometer is an instrument used to measure the density of a liquid. It consists of a float that is calibrated to sink to a certain depth in a liquid, depending on the density of the liquid.

A pH meter is an instrument used to measure the pH of a solution. It consists of a probe that is inserted into the solution and a meter that displays the pH value.

A conductivity meter is an instrument used to measure the electrical conductivity of a solution. It consists of two electrodes that are immersed in the solution and a meter that displays the conductivity value.

A turbidimeter is an instrument used to measure the turbidity of water. It works by measuring the amount of light that is scattered by the suspended particles in the water.

A Secchi disk is a simple instrument used to measure the transparency of water. It consists of a white disk that is lowered into the water until it disappears from view. The depth at which the disk disappears is a measure of the transparency of the water.

A staff gauge is a simple instrument used to measure the stage of a river. It consists of a graduated scale that is attached to a post or structure in the river. The stage of the river is measured by reading the water level on the scale.

A weir is a structure that is built across a river or stream to measure the flow rate of water, control the flow of water, or divert water.

A current meter is a device used to measure the velocity of flowing water. It consists of a propeller or impeller that rotates in proportion to the speed of the water. The discharge of a river can be calculated by measuring the velocity of the water and the cross-sectional area of the river.