Delayed Impact Calculator

This calculator is an Excel workbook programmed with Visual Basic for Applications macro code to perform finite-difference computations for assessment of attenuation and delay dynamics of stream-aquifer system response to groundwater impulse time series input. The spreadsheet estimates impact accrual schedules for well-induced stream depletion and for groundwater return flow scenarios. Single impulse, uniform series, variable series, and annual pattern impulse type options facilitate streamlined input and analysis of a diverse range of occurrence and use patterns, including intermittent pumping. Segregation of response output by stream reach gives location-specific insight useful to surface water administration. Tidy secondary output options include cumulative ratio, response ratio, and period ratio of response to impulse. The workbook (.xlsm) is accompanied by an instruction manual (.pdf) and supplemental materials, primarily consisting of copies configured to match published scenarios. There is also a version in Spanish residing as a separate resource named Calculadora de Impactos Demorados.