Irrigation and Salt Problems in Renmark, South Australia

Abstract

T IJHE deserts of this planet, which cover about 19 percent of the continental surfaces, support only about 5 percent of the world's population. These arid lands have acted as formidable barriers between settled areas and have prevented a more even diffusion of people over the face of the earth. Within these dry lands settlement patterns tend to be ones of clusters and ribbons, reflecting the availability of usable water. Renmark, South Australia, is such a cluster and is one of the many towns along the lower Murray River. Man has attempted to utilize the potential resources of arid lands in many ways, either through irrigation or through mineral extraction in response to industrialization and mechanization. The success of arid lands development through irrigation reflects one of the more dramatic struggles in man's efforts to modify his environment. A narrow margin separates success from failure in this particular endeavor; for the life-giving waters of many rivers also carry the seeds of destruction of agricultural lands. The salt of the earth that furnishes the essential nutrients for plants, man, and beasts also destroys the land whenever the fine balance between overwatering and underwatering is upset. Thus the management of irrigated land in arid environments must be viewed as a critical test of man's willingness and ability to use the knowledge gained from centuries of bitter experience. Nowhere else has there been a more blatant demonstration of land misuse and resource deterioration than in the irrigation districts of arid lands. The Renmark oasis has been selected for study because it is located in a country where the results of scientific research are readily available. Still, the Renmark irrigated lands, like most of the oases along the Murray River, are endangered by the encroachment of salt. This deterioration of agricultural land is truly disturbing when one considers that less than a quarter of Australia has a growing season of five months or more, during which evaporation is not more than three times precipitation, and that a third of the entire con-