Water Pollution Control - A Guide to the Use of Water Quality_14

Nghiên cứu trường hợp mô tả các các phương pháp tiếp cận quản lý chất lượng nước của Sở giao nước và Lâm nghiệp (DWAF) để đảm bảo rằng chất lượng nước mặt trong đập Witbank vẫn còn phù hợp để sử dụng và nguồn tài nguyên này được bảo mật đầy đủ cho tương lai. | Figure Map of the wastewater irrigation system in the Mezquital Valley Mexico Table Irrigation data for the Mezquital Valley 1993-94 Irrigation systems Area ha covered1 Cultivated2 No. of users Water volume 106 m3 a-1 Production value 106 N 3 District 03 Tula 45 214 55 258 27 894 1 148 255 District 100 Alfajayucan 32 118 22 380 17 018 651 85 Private units 5 375 5 450 4 000 96 0 TOTAL 82 707 83 088 48 912 1 895 340 1 Covered area refers to irrigable land with irrigation infrastructure 2 Cultivated area includes some areas with more than one crop per year 3 Average exchange rate for that period was N per US 1 Source National Water Commission CNA Irrigation Districts Headquarters Mixquiahuala Hidalgo Mexico 1995 Table Agricultural productivity in the Mezquital Valley 1990-92 t ha-1 a-1 Crops National mean Mezquital mean Hidalgo State irrigation area Rainfed area Sweet corn Kidney bean Oat Barley fodder Lucerne Sources Agricultural and Hydraulic Resources Secretary SARH Mexico 1994 National values National Water Commission CNA Irrigation Districts Headquarters Mixquiahuala Hgo. Mexico 1995 Mezquital Valley data The wastewater is contaminated with pathogenic organisms and toxic chemicals that constitute a health risk for both farmers and consumers of agricultural products. The principal crops grown are alfalfa maize wheat oats beans tomatoes chillies and beetroot. There is a small but valuable production of restricted crops in the lower section of the Valley District 100 including lettuce cabbage coriander radish carrot spinach and parsley. This crop restriction is part of the management policy for reuse of wastewater with adequate health safeguards. During its use in the Mezquital Valley irrigation districts the Mexico City wastewater a mixture of domestic and industrial waste receives natural land treatment which is equivalent or superior to conventional .