Methodology to quantify crop, irrigation water, and energy linkages in small-holder irrigation systems

Abstract

In India, balancing the conflicting objectives of reducing irrigation water and energy usage, food security, and farmer income, has become very important due to constrained water availability, especially in the context of subsidies for irrigation energy. Policies to reduce water and energy usage are being proposed and tested without sufficient data or analysis in support of the expected outcomes. Some examples of these policies are energy payback schemes or promotion of sprinkler and drip, to control water usage,

Most studies in the water-energy-food nexus (WEFN) area have been conducted using simplified or aggregate data, thus missing the nuances that will arise due to variations in factors such as type of water source, irrigation method, and extent of water usage. This work develops a methodology codifying the interlinkages between crop type, irrigation water usage, and energy usage, at the farm level for Maharashtra state, India. Thus satisfying an important demand in the nexus formulation.

The methodology has two types of parameters. One set of parameters are shown to be uniform across the state. Broadly these are: (i) energy intensity as a function of water source (ii) irrigation depth per irrigation event as a function of irrigation method. These are developed from field measurements.

A second set of parameters incorporate site-to-site variations and are developed through observation. Broadly these are: (i) number of irrigation events per season for a crop (ii) crop to water source correlation.

To apply the methodology in a specific area, the values for the second set of parameters need to be determined through survey. The outputs are energy usage in kWh/ha and water usage in mm in the area for a particular crop. In this paper, the methodology has been applied at five locations each the size of a few villages.

The methodology results illustrate broad trends and distinctions in energy intensity (kWh/m³), energy usage (kWh/ha) and water usage (m³/ha) categorized by monsoonal (kharif), winter (rabi), plantation crops, and sugarcane, and by groundwater and surface water sources. Examples illustrating the potential effects of proposed policies in light of the results are provided. The crop-wise cost of energy as a percentage of profit is calculated to understand the economic value of subsidies.

The methodology reveals the complex irrigation practices and factors that determine energy usage in irrigation. Its generalized nature ensures that it can be applied across the state and is not limited to site-specific cases. The work highlights the importance of conducting research and developing datasets, at a local level.