Irrigation of rehabilitated mine land with circum-neutral mine water

Abstract

Utilizing mine water for irrigation on rehabilitated land will be beneficial for both the mining and agricultural sectors. Mpumalanga has thousands of hectares of rehabilitated land that were considered high-potential agricultural land before mining commenced. Years of research have been done on the use of mine water as an alternative water source for irrigation. The key objective of this study was to determine if circum-neutral mine water can be used for irrigation on rehabilitated land and what factors influence the irrigability of rehabilitated land. A soil survey, using a dryland classification system commonly used in South Africa, was done over an area of rehabilitated land at Mafube Colliery, Mpumalanga. A pivot irrigation system was established on this rehabilitated area to identify and determine the relationships between soil factors and plant growth. High variability in the soil’s physical and chemical properties were identified. The high variability identified in the rehabilitated land combined with the dryland soil potential system was used to identify different sampling areas to determine the factors that influence the irrigability of rehabilitated land. While it was not possible to grow a commercial crop in the first season, weeds were used as a surrogate for crop production to determine which factors affected growth. The results obtained from the weed assessment showed that there was a relationship between both chemical and physical properties of the soil and weed growth. Physical soil conditions, such as restrictive layers and severe compaction had a more significant effect than chemical properties. In the second cropping season, it was possible to establish a pasture mixture under irrigation on the rehabilitated land. Different hypotheses around the irrigability of the rehabilitated land were developed and tested. The final topography of the rehabilitated land proved to be a major factor influencing irrigability. Severe water ponding created difficult growing conditions in the rehabilitated field where poor growth was recorded. It was concluded that when factors like topography and infiltrability are combined with a dryland classification system the accuracy in predicting suitability for irrigation increases. If the correct rehabilitation methodology is followed using the guidelines (Land Rehabilitation Guidelines for Surface Coal Mines), there is no doubt that a more uniform site with acceptable conditions for irrigation and dryland could be created. This study proved that irrigating rehabilitated land with mine water is definitely worth pursuing and will be beneficial for mining and agriculture.