Evaluation of push–pull tracer tests for estimating groundwater velocity in a fractured-rock aquifer; [推-拉示踪试验评估以估计裂隙含水层的地下水流速]; [Evaluation des tests de traçage push–pull pour l’estimation de la vitesse des eaux souterraines dans un aquifère rocheux fracturé]; [Avaliação de testes traçadores push–pull para estimativa da velocidade das águas subterrâneas em um aquífero fraturado]; [Evaluación de los ensayos de trazadores por inyección y extracción para estimar la velocidad del agua subterránea en un acuífero de roca fracturada]

Single-well tests are cost effective to estimate hydraulic parameters compared to multiwell tracer tests, but there are some drawbacks in their accuracy, complicated data analysis and nonuniqueness. As a single-well test, the push–pull tracer test, consisting of injection (or push), drift (or resting), and extraction (or pull) phases, is a cost-effective method that can provide a bulk groundwater velocity in the vicinity of a test well. However, there are limitations to estimating the groundwater velocity because its estimate is sensitive to experimental conditions. In this study, the estimation results of various push–pull tracer tests performed in a fractured-rock aquifer were compared to those based on various hydraulic and tracer tests. Based on a comparison between two approaches, the groundwater velocities estimated with the push–pull tracer test agree reasonably well with those based on other approaches. However, the push–pull tracer test velocity results tends to decrease with increasing drift phase times. This behavior underestimates the groundwater velocity when compared to those estimates from other methods. This difference may be caused by the fact that the mass recovery rate of the push–pull tracer test decreases with increasing drift phase time, which is possibly driven by the relatively high density of an injected tracer. Therefore, appropriate drift phase time is required in order to estimate reasonable hydrogeologic parameters using the push–pull tracer test. © 2022, The Author(s), under exclusive licence to International Association of Hydrogeologists.