Groundwater Transfer Program: North Harris County Regional Water Authority

The North Harris County Regional Water Authority (Authority) accepted wholesale customer requests to build portions of its 2010 Groundwater Reduction Plan transmission system in 2005. The transmission system will convey groundwater from districts with excess supplies (seller districts) to districts with water quality issues or immediate water supply needs, (buyer districts). The Authority established the Groundwater Transfer Program (GTP) in 2004 and designed and constructed three GTP transmission systems, i.e. the North, South and West Systems, in 2005 and early 2006. This paper discusses how the Authority successfully implemented the GTP. Flow monitoring test data was analyzed and the hourly multipliers for certain districts were combined into either composite residential or mixed land use diurnal curves. The University of Kentucky PIPE2000 computer program was used to run static and extended period simulation models of minimum and maximum GTP operating pressures. Control valve stations equalized the daily and seasonal fluctuations occurring outside the GTP transmission system, i.e., within the district's water systems. Fire hydrant tests indicated that seller districts could meet their contract capacities. For buyer districts' water plants, the opening and closing of solenoid valves at the same time resulted in only minor pressure changes in the GTP transmission system, and the system appears to be robust enough to allow almost instantaneous response to flow changes. Water age may be an issue during periods of low demand. The Authority anticipates its operators will conduct routine tests of potable water quality including the chlorine residual content for disinfection. In addition, the Authority may consider requiring that a buyer district's control switches be set to allow the Authority to provide the prime (or base) water supply to each district with the district groundwater wells serving as a secondary supply.