1 Introduction

In Brazil's North-East, the semi-arid interior known as sert/em> (backcountry) is in marked contrast ecologically with the coastal zone (zona da mata) and the transitional zone (agreste). While the coastal zone is humid, receiving more than 1,600 mm of rain per annum, precipitation decreases toward the interior, less than 800 mm falling in the sert The humid coast was originally covered with dense forest, though little of this remains today. In the sert on the other hand, the caatinga the drought-resistant thorn scrub and xerophytic vegetation, predominates.

Such ecological regions have been the basis for different types of human land use, settlement, and economy. On the coast, sugar cane cultivation and sugar production have been important from the early stage of colonization and settlement up to the present. In the transitional zone, intensive farming of livestock and food crops has supported a dense population of peasants. The sert on the other hand, has been characterized by extensive cattle grazing and largescale properties held by absentee owners. Thus, the three regions of zone da mate, agreste, and sert differ in terms of environment, type of economy, and process of development (Andrade, 1968; Saito and Yagasaki, 1987).

While the fragility of the humid tropical environment of Amazonia is attracting worldwide attention, the sert whose ecological conditions and history of human use and occupancy differs substantially from those of Amazonia, is also considered susceptible to the process of desertification. The sert suffers from chronic scarcity of water and recurrent drought. Severe droughts have often caused hunger, poverty, mass migration, and even the deaths of many people as well as of animals.

While the first drought since the Portuguese colonization and settlement was officially recorded in the late sixteenth century in Pernambuco, six droughts occurred in the seventeenth century, fourteen in the eighteenth century, twelve in the nineteenth century, and twelve so far in this century, according to the Superintendency for Development of the North-East (Superintendia do Desenvolvimento do Nordeste) (SUDENE, 1981). Such droughts have become nationally recognized, especially since the late nineteenth century. An influx of people into the interior accelerated with the development of commercial cultivation of arboreal cotton, and the increased population, consequently, further exacerbated the region's susceptibility to drought. Despite attempts by various public organizations and projects to relieve drought problems, the region remains today one of the most underdeveloped sections of Brazil.

For the people in the semi-arid sert maximum use of limited water resources has been their major concern. Traditionally, people took advantage of the brejos, or the humid mountain environment with orographic rainfalls. Farming was practised during the lowwater season in the riverbeds, as the flow ceased, in the moist soil known as vezante. More recently, small reservoirs (aes) were constructed for storing and supplying water. Such reservoirs now constitute an important landscape element of the sert (Saito et al., 1986). These efforts were traditional adaptations of the people to the semiarid environment.

In recent years, the sert is changing, as federal and state governments endeavour to promote regional development by establishing irrigation projects, which attempt to utilize scarce water resources by constructing dams, reservoirs, and irrigation canals and by introducing electric pumps and other irrigation facilities. The land covered with caatinga is being transformed into farmland. Irrigation farming, regardless of the scale and type, gradually - and sometimes drastically - changes agriculture, land use, and rural communities of the sert

Although the contemporary sert in transition can hardly be understood without considering irrigation farming, there is still limited knowledge concerning the process of irrigation development, land-use systems, and agricultural management on the farm and local scales. We also do not know if contemporary development policy will be able to remedy the serts chronic problems. In order to assess the government's irrigation approach for development, the socio-economic and ecological consequences of contemporary irrigation farming need to be scrutinized. Such examinations have to be made on a local scale, based on careful field investigation. Geographers concerned with people, land use, and environment have much to contribute here. An accumulation of case-studies will offer the basis for considering ecologically sound land-use systems and the social well-being of residents, and for reconsidering the regional development policies.

In this paper we intend to examine, on a small scale, the contemporary changes due to irrigation. Presented are two examples of smallscale, spontaneous irrigation farming around reservoirs in Boqueirand Teixeira municos in the state of Para. and a large-scale irrigation development in the middle SFrancisco Valley, around the twin cities of Petrolina and Juiro (fig. 14.1). These areas emerged as important centres of irrigation farming during the past decade or so. We pay special attention to the development process of irrigation, farming types, and land use rotation systems. Details of each case are elaborated in our previous reports (Saito and Yagasaki, 1989,1991; Saito et al., 1991; Yagasaki et al., 1989).