Yn sgil hyn, mae Atodlen 4 i Ddeddf Rheoli Llifogydd a Dŵr 2010 (Deddf 2010) yn cynnwys nifer o ddarpariaethau ar gyfer gwneud cronfeydd dŵr yn fwy diogel drwy ddiwygio Deddf 1975. Un o’r prif ddarpariaethau oedd gostwng y trothwy ar gyfer cyforgronfeydd mawr o 25,000 metr ciwbig i 10,000 metr ciwbig a chyflwyno dynodiad risg uchel ar gyfer y cyforgronfeydd mawr hynny y credir y gallent beryglu bywydau.
Further to this, Schedule 4 to the Flood and Water Management Act 2010 (the 2010 Act) includes a number of provisions to updating reservoir safety legislation by amending the 1975 Act.  Chief amongst these were the reduction of the threshold for large raised reservoirs from 25,000 cubic metres to 10,000 cubic metres capacity and the introduction of the high risk designation for those large raised reservoirs thought to pose a risk to life.