Climate change adaptation: A hydraulic model study to improve the spillway discharge of Giritale reservoir

The Piano Key (PK) spillway constructed at Giritale in 2013, is the first of its kind in Sri Lanka. A capacity enhancement of the Giritale reservoir was required to overcome the frequent water shortages during cropping seasons and droughts. A decision was taken to enhance the capacity by increasing the crest level of the spillway and a new spillway of the PK type was introduced to satisfy this requirement. In this research, a model study was done to improve the discharge efficiency of such a PK spillway. Two models with different sectional arrangements were fabricated and later these were modified basically in crest shape. A total of four different models were tested to simulate the flow behavior over the spillway and the results were analyzed in order to find the head discharge relationship. The research focused on how to obtain a suitable PK model, among the models tested. The conclusion was that model 1b (among the models 1a, 1b, 2a, 2b) was the optimum model for the Giritale project.