The Nashua River Watershed Association will be holding its first Science Saturday of the new year, offering an educational adventure for area children ages 7 to 11, from 1 to 2:30 p.m. on Jan. 12. "The Science of Ice and Snow'' will be led by Mary Marro, the watershed group’s environmental education director. Participants will do experiments with ice and build a snow fort as part of activities held indoors and outdoors at the association’s River Resource Center, 592 Main Street (Route 119) in Groton. The cost is $25, and preregistration is required. To sign up, contact Marro at 978-448-0299, or e-mail firstname.lastname@example.org.