It weighs 10-17 g (0.35-0.60 oz), slightly less than the largest short-tailed shrew. The water shrew’s weight and long tail (67-71 mm, 2.6-2.8 in) (as long or longer than the combined head-body length ...

Remember that, like all animals, shrews need food, water, and shelter, so your best bet is to reduce these three necessities in your yard. And if all else fails, you can (probably) use a shrew trap.