SUBSURFACE TILE DRAINS ARE OFTEN USED IN HUMID AND IRRIGATED AREAS TO LOWER THE WATER TABLE AND THEREBY ACHIEVE A HIGHER CROP YIELD. TILE DRAINS ARE MOST PREVALENT IN THE HUMID MIDWEST AND THE SEMI-ARID WEST, WITH THE LATTER USING DRAINS TO LOWER THE WATER TABLE IN AREAS THAT ARE OVER-IRRIGATED. HOWEVER, WHILE TILE DRAINS PROVIDE MANY BENEFITS TO AGRICULTURE, THEY CAN ALSO BRING ABOUT ENVIRONMENTAL POLLUTION, AS THE DRAINS PROVIDE A DIRECT PATHWAY OF NITROGEN AND PHOSPHORUS FROM CULTIVATED FIELDS TO NEARBY RIVERS AND LAKES. THE ADDED NITROGEN AND PHOSPHORUS IN THE RIVERSE AND LAKES CAUSE AN INCREASE IN MICROBIAL ACTIVITY, WHICH LOWERS OXYGEN LEVELS TO THE POINT OF HARM FOR FISH AND OTHER AQUATIC LIFE.THIS PROJECT WILL DEVELOP A MODELING TOOL THAT CAN TRACK THE MOVEMENT OF NITROGEN AND PHOSPHORUS THROUGH THE SOIL-AQUIFER-TILE DRAIN-RIVER SYSTEM, AND THEN USE THE TOOL TO INVESTIGATE MANAGEMENT PRACTICES THAT CAN BE IMPLEMENTED IN FIELDS TO DECREASE POLLUTION OF NEARBY SURFACE WATER BODIES. THE MODEL WILL BE APPLIED TO ONE WATERSHED IN THE SEMI-ARID WEST (COLORADO) AND TWO IN THE HUMID MIDWEST (IOWA, INDIANA) TO DETERMINE THE INFLUENCE OF CULTIVATION PRACTICES AND CLIMATE PATTERNS ON RESULTS.