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1 Chinnasamy, P.; Hubbart, J. A.. 2014. Measuring and modeling shallow groundwater flow between a semi-karst border stream and Ozark forested riparian zone in the Central USA. Journal of Scientific Research and Reports, 3(6):844-865.

Groundwater flow ; Flow discharge ; Ecosystems ; Forests ; Riparian zones ; Hydrology ; Models ; Soil hydraulic properties ; Stream flow / USA / Missouri

(Location: IWMI HQ Call no: e-copy only Record No: H046360)

http://www.sciencedomain.org/download.php?f=Chinnasamy362013JSRR7711_1.pdf&aid=3574
https://vlibrary.iwmi.org/pdf/H046360.pdf

(0.52 MB)

Aims: Quantitative information is limited pertaining to riparian forest and stream shallow groundwater interactions particularly in karst hydro-ecosystems. Study Design, Place and Duration: Spatiotemporal variability of shallow groundwater flow was monitored along two stream reaches in a riparian Ozark border forest of central Missouri, United States. Each reach was equipped with twelve piezometers and two stream-gauging stations during the 2011 water year (WY). Methodology: High-resolution (i.e. 15 minute) time-series data were analyzed indicating average groundwater flow per unit stream length was -3 x 10-5 m3 s-1 m-1 (losing stream) for the entire study reach (total reach length = 830m) during the 2011 WY. The HYDRUS – 1D groundwater flow model was forced with observed data and outputs were assessed to improve model end user confidence in karst hydrogeologic systems. Results and Discussion: Results indicate rapid groundwater response to rainfall events within two to 24 hours nine meters from the stream. Analyses indicated average stream flow loss of 28% and 7% total volume to groundwater during winter and spring seasons, respectively. During the dry season (June-September), the stream was gaining 95% of the time. During the wet season (March-June), the stream was losing 70% of the time. Based on established assessment criteria, shallow groundwater modeling performance with HYDRUS – 1D was deemed very good (NS = 0.95, r2 = 0.99, RMSE = 2.38 cm and MD =1.3 cm). Conclusion: Results supply greatly needed baseline information necessary for improved understanding of riparian forest management and shallow groundwater transport and storage processes in semi-karst forest ecosystems.

2 Chinnasamy, Pennan; Hubbart, J. A.. 2014. Potential of MODFLOW to model hydrological interactions in a Semikarst floodplain of the Ozark Border Forest in the Central United States. Earth Interactions, 18(20):1-24. [doi: https://doi.org/10.1175/EI-D-14-0015.1]

Hydrology ; Models ; Surface water ; Groundwater flow ; Nitrates ; Precipitation ; Floodplains ; Stream flow ; Forests ; Riparian zones / Central USA / Missouri / Ozark Forest

(Location: IWMI HQ Call no: e-copy only Record No: H046708)

http://journals.ametsoc.org/doi/pdf/10.1175/EI-D-14-0015.1
https://vlibrary.iwmi.org/pdf/H046708.pdf

(1.81 MB) (1.81 MB)

Riparian shallow groundwater and nutrient movement is important for aquatic and forest ecosystem health. Understanding stream water (SW)–shallow groundwater (GW) interactions is necessary for proper management of floodplain biodiversity, but it is particularly confounding in underrepresented semikarst hydrogeological systems. The Modular Three-Dimensional Finite-Difference Ground-Water Flow Model (MODFLOW) was used to simulate shallow groundwater flow and nutrient transport processes in a second-growth Ozark border forest for the 2011 water year. MODFLOW provided approximations of hydrologic head that were statistically comparable to observed data (Nash–Sutcliffe = 0.47, r2 = 0.77, root-mean-square error = 0.61 cm, and mean difference = 0.46 cm). Average annual flow estimates indicated that 82% of the reach length was a losing stream, while the remaining 18% was gaining. The reach lost more water to the GW during summer (2405 m3 day-1) relative to fall (2184 m3 day-1), spring (2102 m3 day-1), and winter (1549 m3 day-1) seasons. Model results showed that the shallow aquifer had the highest nitrate loading during the winter season (707 kg day-1). A Particle-Tracking Model for MODFLOW (MODPATH) revealed significant spatial variations between piezometer sites (p = 0.089) in subsurface flow path and travel time, ranging from 213 m and 3.6 yr to 197 m and 11.6 yr. The current study approach is novel with regard to the use of transient flow conditions (as opposed to steady state conditions) in underrepresented semikarst geological systems of the U.S. Midwest. This study emphasizes the significance of semikarst geology in regulating SW–GW hydrologic and nutrient interactions and provides baseline information and modeling predictions that will facilitate future studies and management plans.

3 Chinnasamy, Pennan; Hubbart, J. A.. 2015. Stream and shallow groundwater nutrient concentrations in an Ozark forested riparian zone of the central USA. Environmental Earth Sciences, 73(10):6577-6590. [doi: https://doi.org/10.1007/s12665-014-3880-7]

Groundwater ; Surface water ; Stream flow ; Nutrients ; Nitrates ; Phosphorus ; Potassium ; Ammonium ; Hydrology ; Riparian zones ; Case studies / Central USA / Ozark Forest

(Location: IWMI HQ Call no: e-copy only Record No: H046717)

https://vlibrary.iwmi.org/pdf/H046717.pdf

(1.12 MB)

Characterizing spatiotemporal variations in surface water (SW)–shallow groundwater (GW) nutrient concentrations is important to predict stream ecosystem responses to disturbance. Unfortunately, there is a lack of such information from mixed-deciduous semi-karst hydro-geological regions. Nitrate (NO3 -), total phosphorous (P), potassium (K) and ammonium (NH4 +) concentrations were monitored in a case study between an Ozark stream and riparian hardwood forest GW over the 2011 water year in the central USA. Average SW NO3 -, P, K and NH4 + concentrations were 0.53, 0.13, 3.29 and 0.06 mg L-1, respectively. Nine meters from the streambank, average GW NO3 -concentration was 0.01 mg L-1, while P, K and NH4 + concentrations were 0.03, 1.7 and 0.04 mg L-1, respectively. Hyperbolic dilution model results indicated that NO3 - and K exhibited dilution behavior, while NH4 + had a concentration effect and P was hydrologically constant. Observed seasonal NO3 - concentration patterns of winter maxima and summer minima in SW (1.164 and 0.133 mg L-1) and GW (0.019 and 0.011 mg L-1) were supported by previous studies yet exhibited distinct semi-karst characteristics. Results indicate that in addition to relatively low residence time, lower nutrient concentrations in GW (relative to SW) may suggest that shallow GW flow processes are important for vegetation removal and retention of nutrients from streams in semi-karst shallow groundwater systems of the central USA.