In addition, the quality of water is altered as man uses it. Return flows from cities and industries contain waste constitutents in various concentrations which affect its suitability for further use. In the broadest sense, pollution can be thought of as any alteration of the quality of water. However, pollution is generally thought of as being some deliterious change in the water quality which renders it unfit for some particular use. Effective water quality management is the goal of water pollution control activities in this country.
Streams serve both as sources of water supply and avenues for the disposal of wastes.
Thus, there is a clear interaction between quantity and quality of water. However, largely due to the agency structure in state and federal government, water quality management and water development activities are usually separated and often delegated to different agencies. As an example, in the State of Texas, the water quality control problems are the major concern of the Texas Water Quality Board, and the water development aspects are handled by the Texas Water Development Board. Although the professional personnel working within these agencies recognize the clear interaction between water quantity and quality, the present institutional structure is not necessarily conducive to the active consideration of this interaction. The State of Texas is not unusual in this regard as many states and the federal government have similar institutional arrangements.