INTEGRATED GROUNDWATER-FLOW AND AGRONOMIC MODELING FOR MANAGEMENT OF DRYLAND SALINITY OF A COASTAL-PLAIN IN SOUTHERN AUSTRALIA

An 'integrated modelling approach' was used to explore a range of opti ons for land management to control dryland salinity. Three models were developed for this study: a numerical groundwater flow model which pr edicts groundwater levels for various land uses; agronomic models quan tifying crop and pasture yield response to shallow saline watertables and seasonal rainfall; and a financial model of farm revenues, costs a nd discount rates. When combined, these provided information on ground water levels, agricultural production, and farm incomes for a 105-km(2 ) site on a coastal plain in southern Australia. The simulations inclu ded current as well as various alternative land management options for a 20-year period. The results indicated that the establishment of dee p-rooted perennial pastures can reduce both rates of groundwater recha rge and the area of salinised land, thereby enhancing productivity. Ho wever, the cost of reclaiming salinised land is high. Compared with cu rrent land management practices, the economic benefit of perennial pas tures is marginal, and depend strongly on future farm commodity prices and discount rates. The methodology described herein represents a hol istic means of dealing with a variety of environmental problems of agr icultural management. Its advantages and disadvantages are also discus sed. (C) 1997 Elsevier Science B.V.