Rainfall Versus Water Balance Components Using R Software: A Case Study on a Micro-watershed in the Mid-lands of Kerala

Quantitative information on an area’s water balance components is essential to plan water management activities. In most cases, these water balance components, viz. rainfall, runoff, soil moisture, groundwater storage, and evapotranspiration, will be missing, especially in the developing world. At the same time, most countries have rainfall data in a reasonably acceptable spatial resolution. Hence, if a relationship between rainfall and other water balance components can be developed, then using these relations, the values of those water balance components can be determined. Hence, a study has been taken up in which important water balance components, viz. rainfall, runoff, soil moisture, the height of groundwater table from MSL, and evapotranspiration, are measured from a watershed, and the relationship between rainfall and other components have been determined through regression analysis. R software was used to determine relationships between rainfall and other water balance components. The Pearson’s correlation coefficient (r) between rainfall vs. runoff was 0.83, rainfall vs. soil moisture was 0.80, rainfall vs. the height of GW table from MSL was 0.72, and rainfall vs. evapotranspiration was -0.64, which indicates a good correlation in the majority of the cases. The relationship between rainfall vs. runoff, rainfall vs. soil moisture, rainfall vs. the height of the GW table, and rainfall vs. evapotranspiration was a polynomial equation with degrees 4, 3, 5, and 3, respectively. The study concludes that it is possible to estimate most other water balance components using the regression estimates by measuring the rainfall. These relationships can be used effectively in water management programs.