ABSTRACT The paper analyses sources of delay in developing environmental interventions to address overallocation of groundwater and water quality degradation for Te Waihora/Lake Ellesmere, a coastal lake in the Canterbury Region of New Zealand. The analysis highlighted the length of time required to collect the science to understand an issue and to formulate and implement policy responses. It also identified delays due to scientific uncertainty, scientific controversies, disregarding science, decision processes, and the response time of the natural system. The absence of clear policy approaches and environmental outcomes in order to implement environmental legislation was a significant source of delay. Delays in implementing environmental interventions led to loss of natural capital with groundwater overallocation reducing flows in groundwater-fed streams and freshwater inflows to the lake, and land use intensification degrading groundwater, groundwater-fed streams, and lake water quality. The extent of development beyond sustainable limits during these delays may have permanently compromised the ability to implement comprehensive environmental interventions.