Flow paths, rainfall properties, and antecedent soil moisture controlling lags to peak discharge in a granitic unchanneled catchment

Abstract

[1] The lag time between peak rainfall and peak discharge is an important index reflecting hydrological properties in a catchment. To characterize lag times, we studied the effects of rainfall properties, antecedent moisture conditions, and flow paths on runoff response in a forested unchanneled catchment, using a hydrometric and hydrochemical approach. Soil moisture, soil pore water pressure, and piezometric surface were monitored. Also, dissolved silica and organic carbon concentrations of spring water and subsurface water were observed. Runoff response was characterized by two types of lag times: a short lag time (<2 hours) or a long lag time (>24 hours). During events with short lag times, saturation excess overland flow was dominant, and the source area was limited to the nearspring area. During events with long lag times, saturated subsurface flow above the soilbedrock interface was dominant, and the source area near the spring was connected to the upslope area via saturated zone above soil-bedrock interface. The spring-hillslope hydrological connection to generate peak discharges with long lag times occurred when the sum of cumulative rainfall and an antecedent soil moisture index, which was derived from initial storage of surface soil layer, was greater than 135 mm. Moreover, the time between the upslope connection of source area and subsequent peak discharge decreased with the average rainfall intensity in the time. We conclude that consideration of antecedent soil moisture conditions as well as rainfall amount and intensity is essential for understanding the regional characteristics of lag times and subsurface water movement.Citation: Haga, H., Y. Matsumoto, J. Matsutani, M. Fujita, K. Nishida, and Y. Sakamoto (2005), Flow paths, rainfall properties, and antecedent soil moisture controlling lags to peak discharge in a granitic unchanneled catchment, Water Resour.

Topographic controls on shallow groundwater dynamics: implications of hydrologic connectivity between hillslopes and riparian zones in a till mantled catchment

“…ASI was determined by first estimating the total water content for each soil moisture sensor profile immediately prior to an event (integration of volumetric water content over depth) and then averaging between sites (e.g. Haga et al, 2005). We identified a threshold relationship between stormflow and the sum of ASI and event precipitation as discussed in a companion paper (Detty and McGuire, in review).…”

Implications of hydrologic connectivity between hillslopes and riparian zones on streamflow composition

“…Hereby, valuable information can be obtained by investigating the response dynamics of river flow, hydrochemistry and shallow groundwater tables to rainfall events. For instance, Haga et al (2005) found a clear shift in lag time (time between peak rainfall and peak discharge) a suitable proxy for the activation of hillslope groundwater flux towards the river system. Many of these studies proved a strong dependency of the rainfallresponses on antecedent moisture conditions (e.g., James and Roulet, 2009;Penna et al, 2011;Sidle et al, 1995;Tromp-van Meerveld and McDonnell, 2006b), which is a proxy for the overall degree of hydrologic connectivity among the active landscape units (e.g., hillslopes) with the river system.…”

Simulation and validation of concentrated subsurface lateral flow paths in an agricultural landscape

“…Buttle and McDonald (2002) found that water flow at bedrock surface occurred in a thin saturated layer. Haga et al (2005) demonstrated that saturated subsurface flow above the soil-bedrock interface was dominant subsurface runoff. Fiori et al (2007) also reported that the principal mechanism for the stream flow generation was subsurface flow along the soil-bedrock interface.…”