matevz 0 Report post Posted February 16, 2016 Hi all, I cant find an explanation on what is the unit that is used in specific yield filed in GMS. Is it the percentage (0-1) or soemthing else. I find getting strange result as the water gets drained faster when Sy is 0.04 in comparisson to where Sy = 0.15. Does anyone has any idea regarding that? Quote Share this post Link to post Share on other sites
Bill Dolinar 1 Report post Posted February 17, 2016 Specific yield is explained on the GMS wiki as follows (http://www.xmswiki.com/wiki/GMS:BCF_Package#Storage_coefficients): specific yield also known as the drainable porosity, is a ratio, less than or equal to the effective porosity, indicating the volumetric fraction of the bulk aquifer volume that a given aquifer will yield when all the water is allowed to drain out of it under the forces of gravity. Quote Share this post Link to post Share on other sites
matevz 0 Report post Posted February 18, 2016 Hey Bill, thanks. I get that, BUT the problem I have trouble understanding is that by my logic, the higher the number (i.e.: efective porosity) the FASTER you can drain the aquifer, right? But...when one inputs the number 0.05 (5%) in comparisson to 0.15 (15%) for Sy (open aquifer) in transient model you get that drainage is a lot faster with the 5%....drawdown is a lot faster in 5% that in 15%....and that i don't understand if it's correct. Thanks, m Quote Share this post Link to post Share on other sites
Bill Dolinar 1 Report post Posted February 25, 2016 With a smaller number the water would drain faster because there is less water to drain. An input of 0.05 means that it only takes 5% of the total cell volume in water to fill the cell, so there is less water that needs to be removed than at 0.15 or 15% total cell volume in water. Quote Share this post Link to post Share on other sites