chapter  2
94 Pages

Methods of Study and Quantitative Assessment of Groundwater Discharge into Seas and Lakes — Advantages and Limitations

Discharge ............................................................................ 63 2.1.3 Complex Hydrologic-Hydrogeological Method Using

Specific Discharge Data..................................................................... 65 2.1.4 Mean Perennial Water-Balance Method............................................ 74 2.1.5 Use of Geospatial Technologies in Mapping and Analysis

of Submarine Groundwater................................................................ 80 2.1.5.1 GIS in Mapping and Spatial Analysis................................ 80 2.1.5.2 Other Geospatial Technologies ........................................... 82 2.1.5.3 Use of GIS in Groundwater Mapping and Modeling ........ 83 2.1.5.4 Study of Inland Seas with GIS........................................... 85 2.1.5.5 Undersea GIS ...................................................................... 86 2.1.5.6 Investigations of Submarine Groundwater Discharge........ 87 2.1.5.7 Future Directions for Research........................................... 88

2.2 Methods of Marine Hydrogeological Investigations...................................... 89 2.2.1 General Remarks................................................................................ 89 2.2.2 Direct Measurements of Submarine Groundwater Discharge

Using Seepage Meters ....................................................................... 95 2.2.2.1 Introduction and Historical Perspective.............................. 95 2.2.2.2 Review of Seepage Meter Styles........................................ 96 2.2.2.3 Lee-Type Seepage Meter .................................................... 97 2.2.2.4 Heat-Pulse Meter................................................................. 97 2.2.2.5 Krupa Seep Meter ............................................................... 97 2.2.2.6 Ultrasonic Meter ................................................................. 99 2.2.2.7 Dye-Dilution Meter........................................................... 100 2.2.2.8 Electromagnetic Seepage Meter ....................................... 100 2.2.2.9 Applications and Environmental Calibrations.................. 101 2.2.2.10 Anomalous Short-Term Influx.......................................... 101 2.2.2.11 Tidal Influences on SGD .................................................. 102 2.2.2.12 Wind, Waves, Currents, and the Bernoulli Effect ............ 105 2.2.2.13 Spatial and Temporal Variations....................................... 106 2.2.2.14 Coastal Zones that can Utilize Seepage Meters............... 108 2.2.2.15 Conclusions and Recommendations for Users................. 109

2.2.3 Isotope and Tracers Techniques....................................................... 110 2.2.3.1 Introduction ....................................................................... 110 2.2.3.2 Uranium and Thorium Series Nuclides............................ 110 2.2.3.3 Helium............................................................................... 113 2.2.3.4 Deliberate Tracer Experiments ......................................... 113 2.2.3.5 Experimental Techniques .................................................. 114 2.2.3.6 Discussion ......................................................................... 116

2.2.4 Study of Anomalies in the Near-Bottom Layer of Seawater and Sediments .................................................................................. 118

2.2.5 Remote Sensing Methods ................................................................ 133

Submarine groundwater discharge (SGD) bypasses river networks and reaches the ocean directly as seepage through its bottom sediments and formations. It is important in the water and chemical balances of the coastal zone (Zektser and Loaiciga 1993; Church 1996; Zektser 2000; Loaiciga and Zektser 2001). Submarine groundwater discharge and its associated chemical fluxes in coastal karst aquifers may be larger than those associated with river discharge, in particular during low stream flow (Moore 1996). Thus grew the interest in developing

methods to estimate SGD accurately (Paulsen et al. 2001). Its estimation, however, poses unique challenges because it often involves the deployment of measurement equipment in coastal waters as well as on land. The highly dynamic nature of groundwater-seawater interactions in the coastal zone hampers the accurate quantification of SGD (Gordon et al. 1996). Relatively short time series and the sparsity of hydrogeological data in most coastal regions constitutes another serious impediment to the accurate estimation of SGD. This chapter presents a review of the hydrodynamic and numerical methods to estimate submarine groundwater discharge. The former included flow nets, piezometers, and seepage meters. The latter consists of numerical simulation with or without coupling of hydraulic and density-driven phenomena governing SGD.