24 - Ecotones and problems of their management in irrigation regions

Summary

ABSTRACT Irrigation is a powerful factor of ecological differentiation of the environment. Changes in hydrological and hydrogeological regimes of a territory lead to the intensification of successions of biotic complexes and the formation of numerous interlinked irrigation ecotones, the functional core of which is the surface water/groundwater ecotone. The concept of irrigation zone ecotone is viewed as ‘a series of multistepped interlocking subsystems’ and considered on the multidimensional point of view.

INTRODUCTION

Irrigation is one of the most ancient activities of people in arid and semiarid regions of the world and it has always been a source of difficult problems (Postal, 1990, 1993; Singh, 1985, 1993; Worthington, 1977). They began six and a half or seven thousand years ago, and by now have become urgent. The area of irrigated land of the world is 222 million hectares and according to the FAO it was 223 million hectares in 1975. There are forecasts that by the end of the twentieth century the area of irrigated lands of the world might reach 400 million hectares. Irrigation is a powerful factor of transformation of the environment (land, water, biotic complexes, ecosystems and landscapes), strengthening its heterogeneity, ecological fragmentation and contrasts (Kassas, 1977). One of the main bases of these phenomena is seepage of water from canals and the creation of surface water/groundwater interactions, influencing the characteristics of land biocomplexes.

About 20 million hectares of land are under irrigation in Central Asia, Kazakhstan (Kostukovskiy, 1988) and the South of Russia.