Tailulu College Water Supply

The Tailulu College project involved a feasibility study of options to improve the existing drinking supply and land drainage at Tailulu College in Tonga. Tailulu College is a school of around 150 students, located 3 km from central Nuku’alofa.  The EWBNZ team includes Thanura Rabel, a water engineer with MWH; Frances Charters, an environmental engineer doing post-graduate study at Canterbury University; and Hajari Thakur, a chartered senior water engineer.  Paul Fonua is the key contact. He is the school principal and head of the Principals’ Association. He is dedicated to run and maintain his school at a high standard that will persist into the future.

Tailulu_watertank.pngThe school gets its water from the town’s reticulated water supply and on-site rainwater tanks. The on-site rainwater collection system stores approximately 50,000 litres. The tank fills to capacity on most rainy days but stored water is quickly used. Pressure pumps feed water into the on-site reticulated systems. The system’s inflow and outflow points are known but the details and condition of the pipes are largely unknown. 

The school’s sports field has poor drainage. Current drainage infrastructure, outflow points, and soil information is largely unknown. The field is located within 200 m of the lagoon which may contribute to a high water table and affect the field’s drainage.

The key issues that were identified are:

  • Insufficient water. This is occurring due to a combination of
    • Low water pressure in the mains supply line into the school means points of water use around the school (e.g. taps) have little or no flow
    • Leakage in reticulation and at fixtures wastes water and further reduces the pressure
    • Rainwater captured in existing tanks on the school site is quickly used.
    • Recurring flooding of the school fields occurs when it rains and can take days or, in extreme cases, weeks to dry. The school can’t use the fields when they are flooded and the stagnant water is unhealthy.
  • Recurring flooding of the school fields – this occurs when it rains and can take up to several days or, in extreme cases, weeks to dry. The school can’t use the fields when they are flooded and having this stagnant water lying around is unhealthy.

Shreejan Pandey, EWB, gathered data on a recent visit to the college as part of another EWB project. From this information we have identified key gaps and sent a series of questions to Paul Fonua. These questions include the expected future school roll, sources of water demand (indoor and outdoor use), expected changes in demand sources in the future, and more details of the current rainwater harvesting system.

We are also currently designing field measurements and checks that we will request Paul and his staff to perform. For example, identifying where demand occurs around the school (spatial distribution), the groundwater depth in the fields, the soil type, and the high tide elevation.

With more information about the existing system, the nature of the issues, and local site characteristics (rainfall, soils, groundwater), we can establish design parameters. Then we will develop options and estimate the cost for each. Options can then be evaluated on their advantages, disadvantages, and cost implication. Our goal is to make recommendations on the viable options for (a) improving the water supply, and (b) improving field drainage.