Hydraulic head, as a layman would know it and feel it, is the pressure with which water shoots (or trickles) out when a bathroom or kitchen faucet is turned on. In physical terms, the water pressure in your domestic faucet is only kinetic energy manifesting itself. This kinetic energy is a converted form of the potential energy (or hydraulic head) that builds up in water when it is pumped up to its perch in the overhead water tank. This potential energy, in turn, is the converted form of the electrical energy involved in operating the pump which forces the water upwards. So, hydraulic head = energy. Which is to say that taking a bath is probably as energy-consumptive as running a light bulb for a certain amount of time, even if it is just cold water. But few people who have had running water all their lives will ever fully appreciate the value of a healthy hydraulic head. My home in Rajasthan for a couple of years had a community hand-pump as the only source of water. In peak summer, when groundwater levels dropped downwards of 110 feet and every drop had to be drawn up manually, one couldn't but marvel at the miracle that a self-flowing faucet is.

The remarkable thing about a hydraulic head is that it is an indicator of more than just availability of electricity and water. Much political machination goes in to aid or debar the distribution of hydraulic heads in society. For example, the valley people of Narmada fought for years to not allow the lowlanders of Gujarat to create the dam they needed to build up enough hydraulic head to send water all the way to Kutch. Urban elite in India whine their heads off about groundwater exploitation when farmers throw in deep tubewells to get just enough head to water a field of rajka. At the same time, most of India’s success stories have been built around robust hydraulic heads. The Gangetic plains would never have been the cradle of civilization if Bhagwan Shiv had, instead of tying up Ganga in his locks, allowed her to expend all her hydraulic head in one fell swoop to the ground. Closer in time, the Green Revolution was arguable based on the heads created behind Nehru’s temples, and Kurien’s brilliant White Revolution in Gujarat was built on the hydraulic head behind the Mahi dam.

Verily, the hydraulic head (which is measured in metres or feet) is as robust an indicator of prosperity and wellness as Friedman’s Index of Economic Freedom or such. Why not just say "Kerala is 3 feet happy while Bihar is only a few inches happy" instead of parading acronyms to explain simple stuff like the economists do? Furthermore, little is required to survey a population for this indicator. No fancy PhDs, no intricately designed questionnaires, no deligent interviewers, and no patient interviewees are needed. Just a batallion of boys with a bucket and a stop watch to measure faucet discharge running from door to door and reporting their findings to a babu armed with a calculator and the hydraulic energy formula and, lo and behold, you have a barometer of prosperity stuck right into any society’s armpit.