Spring Responses to Storms and Seasonal Variations in Recharge in the Middle Atlas Region of Morocco

Abstract:

Springs in the Middle Atlas Mountains of Morocco are significant sources for public water supply, and understanding a spring’s response to storm events and seasonal variations can provide insight on the sensitivity of that spring’s flow to climate change. From 18 March 2014 to 15 May 2015, at 15-minute intervals, water temperatures and water levels were measured at three springs (Ribaa, Sidi Rached, and Zerouka), and water levels were measured at Sidi Rached and Zerouka. From 19 March 2014 to 28 March 2015, daily water samples were taken at Zerouka for analyses of deuterium and oxygen-18. Temperature responses varied between the springs. Sidi Rached showed a time-lagged seasonal signal, with minima in May and June and maxima in October, on which responses to individual storms (inferred from water-level spikes) were superposed. Ribaa showed two cycles of temperature fluctuations from April to November 2014, followed by more flashy behavior from November 2014 to May 2015. Event-related temperature fluctuations were as much as 0.36 C for Sidi Rached and 0.74 C for Ribaa. Duplicate thermistors from different manufacturers showed different behaviors at Zerouka: one showed long-term downward drift from ~ 12.6 to 12.3 C, whereas the other was stable within +/- 0.06 C. Subtle temperature fluctuations superposed on the long-term trends may reflect responses to individual storms at Zerouka. Preliminary stable-isotope data from Zerouka indicate daily fluctuations of as much as 0.5 per mil ¹⁸O and 3.9 per mil ²H superposed on longer-term upward and downward trends (on the order of 2 months). Acquisition of meteorological data from the study area and statistical analyses are pending, but initial results indicate a variety of spring behaviors suggestive of differences in hydraulic connectivity within each spring basin.