Improved quantification of evaporation from industrial pollution control dams

Abstract

Evaporation is a critical component of water balance calculations at mining and industrial sites, particularly in water-scarce regions with high evaporative demand, such as Southern Africa. While direct evaporation measurement provides high accuracy, it is often prohibitively expensive. As a result, empirical estimation methods are commonly used, though their accuracy and applicability under real-world constraints are not well understood in this context. This study presents a practical and cost-conscious approach for estimating daily evaporation using empirical methods, validated against direct measurements from a long-term storage dam. Results show that temperature, solar radiation, rainfall, and wind are most reliable when measured on-site. Among the empirical models tested, the Hargreaves method offers a simpler yet sufficiently accurate alternative to the Penman-Monteith equation. Sensitivity analysis reveals that temperature (for Hargreaves and Penman-Monteith) and solar radiation (for Penman-Monteith) exert the greatest influence on estimated evaporation, suggesting that these parameters should be prioritised in data collection when resources are limited. The study provides practical guidance for improving water balance modelling in industrial contexts, particularly where direct measurements are not feasible.