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 network analysis system (IDNAS) for agricultural drainage management. In the ®rst paper, the system components, functions and implementation were presented. This paper focuses on the system applications to agricultural drainage management, particularly on the acid drainage problems in an estuarine acid sulfate soil ̄oodplain environment. Four case studies are presented which 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 ̄ow) to the watershed outlet and the drainage areas that contribute to the isochrones; (2) assess the capacity of the existing drainage network; (3) estimate the accumulated acidic pollutant (total pollutant load) at an outlet within given times; and (4) simulate acid out ̄ow events and predict the amount of acidic pollutant discharged to the river system associated with each event. The results of these case studies can be used for ef®cient assessment of acid control practice and for development of better management policies. It is demonstrated that the IDNAS can be used effectively to simulate the water balance and drainage network over an agricultural watershed, and to aid the drainage management in an estuary ̄oodplain environment. # 2000 Elsevier Science B.V. All rights reserved.