ENVIRONMENTAL IMPACT OF UNTREATED WASTEWATER IRRIGATION IN KATHMANDU VALLEY: A REVIEW

Journal: Environmental Contaminants Reviews (ECR)
Author: Samita Thapa

This is an open access article distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Doi:10.26480/ecr.02.2020.71.75

ABSTRACT
Irrigation water scarcity is a common problem in agriculture throughout the world. With 80% of the annual precipitation occurring between June and September, leaving the remaining eight months relatively dry, Nepal is said to be water stressed. Increasing population in and around the Kathmandu valley generates a huge amount of waste water. This wastewater is dumped directly into the local water bodies. The main river system of Kathmandu valley is heavily polluted with wastewater and is used to irrigate the nearby agricultural land to produce food for the urban population. Easily accessible and available all year round, about 80% of irrigation inside the Kathmandu valley is done with wastewater. Some studies report an increase in yield attributed to increased nutrient content, while others report drying and wilting symptoms in crops. Soil acidification, salinization, increased heavy metal concentration, coliform bacteria counts, etc., are some concerns that need to be addressed before applying wastewater directly on fields. This article aims to analyse the extent and possible effect of wastewater irrigation on soil in Kathmandu valley. Parameters like Sodium adsorption ratio, potassium, total nitrogen, coliform count, bicarbonate, chloride, phosphorus, cadmium, etc., and their effect on soil profile are reviewed from available literature.

KEYWORDS
Heavy metals, Soil, Water scarcity, Bagmati