Groundwater recharge in Pleistocene sediments overlying basalt aquifers in the Palouse Basin, USA: modeling of distributed recharge potential and identification of water pathways

Abstract

Groundwater levels in basalt aquifers around the world have been declining for many years. Understanding water pathways is needed for solutions like artificial drainage. Water supply in the Palouse Basin, Washington and Idaho, USA, primarily relies on basalt aquifers. This study presents a combination of modeling and field observations to understand the spatial distribution of recharge pathways in the overlying Pleistocene sediments. A spatially distributed model was used to quantify potential recharge rates. The model shows clearly that recharge predominantly occurs through non-argilic soils and soils that are not underlain by fine-grained sediments, i.e. the upper area of the watershed. A field survey was conducted to determine recharge pathways from this area. It revealed 83 perennial springs. Drillings near springs showed connection of coarse-grained layers within the fine-grained Sediments of Bovill to these springs. Such layers, with streambed-like features, act as paleo-channels. Water from one of these coarse-grained layers had a similar electrical conductivity (200 μS cm -1 ) to water from a downstream perennial spring, also suggesting the existence of a lateral conduit for deep percolation water.

Long term agroecosystem research experimental watershed network

“…(Dijksma et al, 2011; Gasch et al, 2015; Ibrahim & Huggins, 2011; Kelley et al, 2017; Rittenburg et al, 2015)…”

Isotopic Discrimination of Aquifer Recharge Sources, Subsystem Connectivity and Flow Patterns in the South Fork Palouse River Basin, Idaho and Washington, USA

“…This limited variation in relatively negative water isotope values for Ca-HCO 3 groundwater in shallow-to-intermediate depth Central wells indicates a recharge signal more aligned with modified (evaporation effect) snowmelt or the modeled precipitation signal for the Palouse Range than the more positive Basin precipitation (USNIP), mid-Basin surface water (Surface Connection) or more negative Deep water (Figure 4). This "Shallow" source water also has similar δ 13 C values (−15.9 to −13.1 ; Figure 5), δ 34 S values (9.7 ± 2.2 ; Figure 6), alkalinity values (110 to 150 mg/L) and groundwater temperatures (12)(13)(14)(15)(16)(17)(18)(19) • C) between those of groundwater from Surface Connection and Deep wells. It is likely this group of wells represents a source water mixture influenced to varying degrees by the Deep source and the Surface Connection source.…”

“…Fall/winter/spring precipitation/snowmelt is the dominant seasonal source of potential recharge because of limited rainfall and high evapotranspiration during summer [31]. Basin recharge is expected to occur primarily along the eastern margin where infiltration/percolation pathways can allow water to enter the Latah and CRBG formations [7,16]. The difference in elevation between the USNIP site and the Palouse Range would produce differences in the isotopic signal of potential recharge from precipitation and snowmelt [26].…”

“…Previous studies have suggested that groundwater recharge is entering the Wanapum and Grande Ronde aquifers through pathways beginning in sediments along the eastern margin of the Basin [7,8,16]. Due to low soil permeability and limited connectivity between basalt flows [8,9,16], it is unlikely for diffuse recharge to occur with infiltration of precipitation. The combination of variable permeability, basalt fracture termination and discontinuity of basalt flows and interbedded sediments produces a heterogeneous and anisotropic aquifer(s) matrix.…”

Hydropedology in Seasonally Dry Landscapes

“…Where buried soil layers consist of argillic and/or fragipan horizons, long pore-water residence times suggest that these uplands do not serve as active recharge zones (O'Geen et al, 2002;Dijksma et al, 2011). Through research over the last ten years, it has become apparent that the probability of groundwater recharge flow paths through soils having argillic or fragipan soils is very low.…”