Return flow analysis in large paddy rice irrigation scheme: Kibimba.

Abstract

Downstream communities are the most affected by waterlogging problem and downstream quality degradation caused by irrigation return flow through inefficient irrigation. As a sustainable water management measure of mitigating the impacts of climate change of water scarcity, the study thereby investigated the quantity of return flow that waterlogged at the downstream of the canal, assessed the quality of the return flow and modelled the quantity and quality of return flow. The methods applied were field measurement, IWQI, ArcGIS and water quality sampling. A Hydrolab - H2O multiprobe sensor, water quality measurement sensor and Discharge metre were the materials used in this study. A return flow coefficient of 33% was investigated as the quantity of return flow that waterlogged at the downstream of the canal. During the assessment of the quality of the return flow, it was revealed that it was restricted (unfit) for irrigation due to the extent of degradation. The modelling results of return flow quantity and quality also revealed that 69% variability in return flow quality was explained by the regression equation based on return flow quantity, yielding a strong positive correlation between quantity and quality of return flow with an r – value of 0.830. Therefore, the model used was valid with generated p – values for the overall, being less and equal to 0.05. In general, the results obtained in this research were in agreement with the results observed in the previous related research studies. Return flow analysis in the large paddy rice irrigation scheme in Kibimba was successful. The results generated shall enable Kibimba to address the waterlogging problem and the downstream quality degradation, if implemented. Further research was recommended in the reuse of return flow for irrigation to observe the effects on paddy rice growth and yield.