The increased demand for water and the attention given in recent years to the deterioration in the quality of our nation's water resources have been accompanied by an increased demand for water resources data. The search for appropriate data has spotlighted the fact that there are numerous deficiencies in the data base. One of the deficiencies is related to the quality of the data because frequently there are few if any indicators as to how good or bad the data actually are. Another deficiency is lack of comparability and compatibility of water data that have been collected by different organizations. Much of this deficiency can be attributed to differences in acquisition methodologies and in handling procedures. One can appreciate the magnitude of these problems when it is realized that there are about 30 federal agencies, hundreds of state and county agencies, and an unknown number of other organizations that collect water data.