Dynamic analysis of groundwater discharge and partial-area contribution to Pukemanga Stream, New Zealand

Abstract

Abstract. The proportion and origin of groundwater contribution to streamflow from agricultural catchments is relevant to estimation of the effects of nitrate leached from the soil on the quality of surface waters. This study addresses the partitioning of streamflow contributions from near-surface runoff and from groundwater, each with different contributing land area, on a steep pastoral hillslope in a humid climate. The 3 ha headwater catchment of the perennial Pukemanga Stream, in the North Island of New Zealand, was instrumented for continuous observation of climatic data, streamflow and groundwater level. The dynamics of groundwater levels and groundwater contribution to streamflow were analysed by means of a one-parameter, eigenvalue-eigenfunction description of a 1-D aquifer model. Model results for seven years of daily data predict that 36-44% of the topographical catchment contributes groundwater to the stream. The remaining groundwater generated within the catchment contributes to streamflow outside the catchment. Groundwater was calculated to be 58-83% of observed annual streamflow from the topographical catchment. When the smaller groundwater catchment is taken into account, the groundwater contribution to streamflow is 78-93% on a unit area basis. Concurrent hourly data for streamflow and groundwater levels at two sites indicate the dynamic behaviour of a local groundwater system. Groundwater flow dynamics that support the perennial nature of this headwater stream are consistent with the size of the groundwater body, porosity of the subsurface material, and hydraulic conductivity derived from partitioning of streamflow contributions.

Estimating catchment-scale groundwater dynamics from recession analysis – enhanced constraining of hydrological models

“…A5). These latter statements assume, of course, that the topographical catchment area and that of the aquifer are equal, an assumption that does not always hold (Bidwell et al, 2008).…”

“…A single linear reservoir is, however, too simple for describing the variability and non-linearity of hydrological response (Brutsaert and Nieber, 1977;Lindström et al, 1997). Some groundwater models conceptualise the stream-aquifer inter-4964 T. Skaugen and Z. Mengistu: Estimating catchment-scale groundwater dynamics from recession analysis actions as the drainage of an infinite number of independent linear reservoirs (Sloan, 2000;Pulido-Velasquez et al, 2005;Bidwell et al, 2008;Rupp et al, 2009). This comes as a result of solving the linearised Dupuit-Boussinesq equation for saturated flow as an eigenvalue and eigenfunction problem.…”

“…In this model, the dynamics of runoff are modelled using linear reservoirs (unit hydrographs -UHs) arranged in parallel, a principle which resembles the stream-aquifer interaction model described by, for example, Bidwell et al (2008). The UHs are turned on and off according to the level of saturation in the catchment.…”

Characteristics and controls of variability in soil moisture and groundwater in a headwater catchment

“…The hydrology of the riparian zone may be particularly sensitive to groundwater connections (Vidon and Hill, 2004). While previous NZ catchment studies have measured groundwater response in a limited number of locations (Bidwell et al, 2008) or without simultaneous surface water measurements (Gabrielli et al, 2012), a joint data set of spatio-temporal surface and groundwater measurements did not previously exist in New Zealand.…”

Groundwater -- surface water interaction under the effects of climate and land use changes.

“…Kingdom, Germany, Belgium), where more precipitation occurs during winter as rainfall, the mean annual groundwater contribution to stream flow is 30% -40% (Soulsby et al, 2006), 30% (Krause et al, 2007), 60% -70% (Koeniger et al, 2009), and 71.9% Yimam (2010); in the mountainous region, where snowmelt and glacier melt provide a significant surface runoff, the mean annual groundwater contribution to stream flow is 75% (Clow et al, 2003), and 67% -74% (Hood et al, 2006), 70% (Hannah et al, 2007); in Cuito River watershed in Angola, where the terrain is hilly and the climate is arid, the mean annual groundwater contribution to stream flow ranges from 74% to 80% (Hughes, 2004); in a steep headwater catchment in New Zealand in humid climate, the mean annual groundwater contribution to stream flow is 87% (Stewart et al, 2007), and 78% -93% (Bidwell et al, 2008). With respect to the mean annual groundwater contribution to stream flow during the reference period, the mean annual groundwater contribution to stream flow from 2012 to 2016 under the A2 and B1 scenarios is expected to decrease by 3.3% and 1.8%, respectively, due to the increased precipitation (on average 6.1% under the A2 and 3.6% under the B1 scenarios) and temperature (on average 0.64°C under the A2 and 0.36°C under the B1 scenarios) predicted, with respect to that under the reference period.…”