Compare with dichondra. Notice the cutout in the leaf that distinguishes it from hydrocotyle which grows in a wetter environment. dichondra is apparently grown as a turf alternative… I tried letting it grow at my house to see if it would produce an attractive patch, but alas… it died. So… i would advise turning off the sprinklers… that should kill the dichondra and that nasty exotic turf also. Although… it probably rains up where you are… http://www.ipm.ucdavis.edu/TOOLS/TURF/TURFSPECIES/dichondra.html