An integrated drainage network analysis system for agricultural drainage management. Part 2: the application

This is the second of two papers that elaborate on an integrated drainage n etwork analysis system (IDNAS) for agricultural drainage management. In the first paper, the system components, functions and implementation were pres ented. This paper focuses on the system applications to agricultural draina ge management, particularly on the acid drainage problems in an estuarine a cid sulfate soil floodplain environment. Four case studies are presented wh ich address practical drainage management tasks in an acidic sugarcane area in northern New South Wales, Australia. These tasks are: (1) determine the isochrones (contour lines of equal time of flow) to the watershed outlet a nd the drainage areas that contribute to the isochrones; (2) assess the cap acity of the existing drainage network; (3) estimate the accumulated acidic pollutant (total pollutant load) at an outlet within given times; and (4) simulate acid outflow events and predict the amount of acidic pollutant dis charged to the river system associated with each event. The results of thes e case studies can be used for efficient assessment of acid control practic e and for development of better management policies. It is demonstrated tha t the IDNAS can be used effectively to simulate the water balance and drain age network over an agricultural watershed, and to aid the drainage managem ent in an estuary floodplain environment. (C) 2000 Elsevier Science B.V. Al l rights reserved.