Hydrology work

8 June 2017

The Water Division of WATSAN is conducting hydrology work looking at flows of streams in catchments on Rarotonga and carrying out maintenance and calibrating rain gauges installed in the five catchments on the island and on Mount Te Kou.  The staff have visited Mauke and Mitiaro to carry out groundwater testing and install automated rain gauges of which Mauke and Mitiaro are the last to receive the gauges.  Hydrology Technician Timothy Tangirere and trainer, Pete Mason a Hydrologist from the National Institute of Water and Atmosphere (NIWA) in New Zealand have done the majority of the work. 

Tangirere has been working and training up in the field of Hydrology for two years.  The strategic plan for the division is to ensure that the hydrological information necessary for infrastructure works and water supply is obtained.  The data collected is used by engineers to design water infrastructure needs on Rarotonga and the Pa Enua.  “We cannot manage what we can’t measure”, says Water Division Manager, Wilson Rani.  “For example, we can’t design appropriate intakes without knowing our water production” he adds.

While on Mitiaro and Mauke, the small team have pumped out monitoring wells on both islands that were done as part of a drilling project in the outer islands in the mid 2000’s.  The project was to look for ground water to supplement the water supply.  “It is important not to overharvest groundwater as it is a critical part of a balanced ecosystem so any extraction of groundwater should only be when it is absolutely necessary and in a properly managed manner”, says Tangirere.  Conductivity tests for salinity were run on the water samples pulled from the monitoring wells, from different depths of the groundwater.  “This work is important because the islands only have rainwater and groundwater to rely on so it is imperative that the quality of the groundwater water is known in the outer islands for the safety of public health”, adds Tangirere.  Once the team have finished the investigations, the data will be processed and reported back to the public on the outcomes. 

Lastly, automatic rain gauges have been installed which continuously measure rainfall so trends over time can be seen.   The Water Division takes advantage of other colleagues travelling to the outer islands to switch the counters which is a very easy task and bring back the data to Rarotonga.