We know that some modern and also ancient coral reefs and carbonate mounds may be intimately associated with the sub-surface hydrology. To the west of the Great Barrier Reef (GBR), there is located a massive groundwater basin trapped in The Great Artesian Basin (GAB). Even though there is a mountain chain between these two entities, there may be a possiblity that some of the artesian water may be leaking out on the seafloor immediately below or adjacent to parts of the GBR.
For a discussion of similar aspects, please see: Hovland (1990) and Hovland (2008) provided attached.
Karst as well as fractured substrates can sometimes differ from surface hydrology boundaries, and discharge under pressure as mentioned. While in Missouri, I was in contact with Tom Alley who did fluorescent dye studies in karst terrain. He found instances where dye was added to underground spring network, and portions showed up in an adjacent stream system outside of the conventional surface hydrology boundary. Karst water quality springs often have a signature related to flow. My researchgate paper on Missouri spring water quality in karst geology may be of some interest. I have commented to similar questions of other researchers related to the possibility of Karst springs with marine or estuarine connections. We also had a few artesian springs that discharged to upland marine terraces on the Francis Marion National Forest in coastal SC, USA (this area in geologic time was several hundred feet under water). I do not know specifics of your area of interest, so consultation with geologist or hydrogeologist might help evaluate the potential for or help develop plan to assess connectivity, or help determine if there are other potential sources.
Well,
The answer is (pressure dependent), as in your discussion the groundwater is occurred in an artesian condition, meaning the groundwater pressure is above atmospheric pressure. In other words, there are good conditions of high chance for mixing mechanism between groundwater and sea floor sediment water due to diffusion and dispersion processes, which may be neglected in a case of lowering pressure in the coastal aquifer due to shortage in recharge water (low rainfall intensity).
Sincerely
Karst as well as fractured substrates can sometimes differ from surface hydrology boundaries, and discharge under pressure as mentioned. While in Missouri, I was in contact with Tom Alley who did fluorescent dye studies in karst terrain. He found instances where dye was added to underground spring network, and portions showed up in an adjacent stream system outside of the conventional surface hydrology boundary. Karst water quality springs often have a signature related to flow. My researchgate paper on Missouri spring water quality in karst geology may be of some interest. I have commented to similar questions of other researchers related to the possibility of Karst springs with marine or estuarine connections. We also had a few artesian springs that discharged to upland marine terraces on the Francis Marion National Forest in coastal SC, USA (this area in geologic time was several hundred feet under water). I do not know specifics of your area of interest, so consultation with geologist or hydrogeologist might help evaluate the potential for or help develop plan to assess connectivity, or help determine if there are other potential sources.
It seems the mountain range is important in keeping the groundwater from the reef in the East. A more likelly route for the groundwater is to the North and South, where you actually find hot springs?
Thanks, Ketil,
this is interesting news to me. But, I do not understand why you put a question mark behind the last word? Are you telling us that there are 'actually hot springs' in the area to the south and north of the GBR, or are you asking a question? This puzzles me.
No the question mark is meant the uncertainty of the groundwater directions..
Dear mates,
I believe that what you meant is Wonky Holes as Wang et al (2007) pointed out with referring to Stieglitz (2005) as quoted below
" There is also a possibility that freshwater discharge exists in deeper areas of the shelf. There is circumstantial evidence that freshwater springs known locally as ‘Wonky Holes’ are intermittent freshwater springs that occur primarily north of the area of interest in this paper (Stieglitz 2005). Studies of these features indicate that they occur in regions where a coastally attached sediment wedge overlays ancient river channels on the shelf and may still be connected hydraulically to the coastal plains (Stieglitz 2005). Measurement of salinity over the ‘Wonky Holes’ indicate that if Wonky Holes are springs, they certainly do not produce large quantities of fresh water (if any) in periods of dry weather (T. Stieglitz and P. Ridd, James Cook University, unpubl. data). They therefore probably do not contribute large volumes of water to the lagoon in the late dry season, or in years when there is minimal wet season rain. Additionally, very few ‘Wonky Holes’ are documented in the Townsville region except in the extreme north of the region considered in this work, i.e. north of transect V " Please see Article Flushing time of solutes and pollutants in the central Great...
andArticle Submarine groundwater discharge into the near-shore zone of ...
My study was during Australian dry winter season (August to October) during which precipitation is negligible with extreme evaporation driving hypersaline water in the inshore GBR to be the driver for cross-shelf exchange flow. Hence, if the Wonky Holes indeed exist during this particular season it might only provide modest quantity of freshwater leading to insignificant water exchange compared to density-driven circulation by hypersalinity
Best,
G
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