Municipal stormwater-drainage rezoning and informal greywater-reuse cooperative formation in Kumasi sub-metros: a boundary-discontinuity estimation of drainage-catchment thresholds

Municipal stormwater-drainage rezoning in Kumasi sub-metros creates sharp administrative boundaries between drainage catchments, yet the consequences of these boundaries for informal greywater-reuse cooperative formation remain unexamined. Because no observational data on cooperative formation are available, the study characterises the operating characteristics of the before-after-control-impact estimator under a declared variance structure with an intraclass correlation of 0.64, between-cluster standard deviation of 6.0 and residual standard deviation of 4.5. Power was estimated across 2000 design cells for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The analysis indicates that 54 clusters are required to detect a 5-percentage-point effect at 80 per cent power. The framework proposes that drainage-catchment boundaries function as discontinuous institutional thresholds, and it specifies the design conditions under which boundary-discontinuity estimation can identify cooperative-formation responses to rezoning. The contribution is a methodological apparatus for studying the intersection of municipal drainage governance and informal water-reuse organisation in African secondary cities.