Sự khan hiếm nước và hạn hán là một trong những trở ngại nghiêm trọng nhất phát triển nông nghiệp và một mối đe dọa lớn đối với việc môi trường trong các khu vực khô. Nông nghiệp trong các khu vực khô chiếm hơn 75% tổng mức tiêu thụ nước. Với sự gia tăng nhanh chóng trong nhu cầu, nước sẽ ngày càng phân bổ lại đi từ nông nghiệp và môi trường. Mặc dù tình trạng khan hiếm, nước tiếp tục được sử dụng sai mục đích. khai thác mỏ nước ngầm hiện nay là một thực tế phổ biến, mạo hiểm cả nước dự trữ. | 8 The Role of Water Harvesting and Supplemental Irrigation in Coping with Water Scarcity and Drought in the Dry Areas THEIB Y. OWEIS CONTENTS I. Introduction. 192 II. Supplemental Irrigation. 193 A. Optimization of Supplemental Irrigation. 196 1. Deficit Supplemental Irrigation. 196 2. Maximizing Net Profits. 198 3. Cropping Patterns and Cultural Practices. 198 B. Water vs. Land Productivity. 199 III. Water Harvesting. 200 A. The Concept and Components of the System. 200 B. Water Harvesting Techniques . 203 1. Micro-Catchment Systems. 203 2. Macro-Catchment Systems. 207 C. Water Harvesting for Supplemental Irrigation . 210 191 Copyright 2005 by Taylor Francis Group 192 Oweis IV. Conclusions. 211 References. 212 I. INTRODUCTION Water scarcity and drought are among the most serious obstacles to agricultural development and a major threat to the environment in the dry areas. Agriculture in the dry areas accounts for more than 75 of the total consumption of water. With rapid increases in demand water will be increasingly reallocated away from agriculture and the environment. Despite scarcity water continues to be misused. Mining groundwater is now a common practice risking both water reserves and quality. Land degradation is another challenge in the dry areas closely associated with drought-related water shortage. Climatic variation and change mainly as a result of human activities are leading to depletion of the vegetation cover and loss of biophysical and economic productivity. This happens through exposure of the soil surface to wind and water erosion and shifting sands salinization of land and water logging. Although these are global problems they are especially severe in the dry areas. Two major environments occupy the dry areas. The first is the wetter rain-fed areas where rainfall is sufficient to support economical dry farming. However because rainfall amounts and distribution are suboptimal drought periods often occur during one or more stages of crop growth .
