In sandals, with his camera in a dry bag around his neck, Paul Tashjian crosses the Rio Grande north of Albuquerque. On a Monday afternoon in mid-June, the river’s muddy waters slide past the Pueblo of Sandia and the Village of Corrales at about 40 cubic feet per second — four percent of the normal flow for this time of year. Barely getting his shins wet, Tashjian, a hydrologist, heads to what’s called an outfall on the east side of the river.