Modelling Water Resources in the Ancient Indus Valley City of Dholavira and Lessons Learnt

Abstract

Dholavira was a part of the Indus Valley Civilisation known for its efficient town planning and water conservation. Dating back to 2600 BC, when cast iron and steel pipes were sporadic and rather scarce, unskilled builders within the city cut trapezoidal channels for water to flow into the city. These channels were excavated from natural earth with low Hazen–Williams constant (0.01) avoiding major and minor losses. Modern materials like cast iron when used cause excessive frictional losses inside the pipes, resulting into loss of hydraulic gradient. The most crucial fact that this paper establishes is a new calculation of the city’s natural hydraulic gradient which is estimated to be about 12–20 m. This is sufficient for an efficient distribution of water from reservoirs to the inner dwellings of the city. The reservoirs with a height of 22–24 m could supply a unit demand of 11–16 MLD and store 2–3 MLD. The hydraulic gradient obtained from a Bentley WaterGEMS simulation was around 24 m which was close to the natural hydraulic gradient. The Scenario energy cost for Dholavira was also calculated using an energy pricing model which was then compared to modern-day water management systems. When superimposed on the 2600-BC-old distribution channel, it gave a savings of about 7.02 million USD annually in terms of energy efficiency.