Is the problem, Ori, that you think a pulse cannot be a one-time event? If so, you are mistaken - this is one of the meanings of 'pulse'.
pulse
noun
1. the regular throbbing of the arteries, caused by the successive contractions of the heart, especially as may be felt at an artery, as at the wrist.
2. a single pulsation, or beat or throb, of the arteries or heart.
3. the rhythmic recurrence of strokes, vibrations, or undulations.
4. a single stroke, vibration, or undulation.
5. Electricity. a momentary, sudden fluctuation in an electrical quantity, as in voltage or current.
Detonating an explosive device in air or water produces a pulse of pressure; a nuclear device produces pulses of heat, light, radiation and air pressure.
It is... "designed to bring the river's dwindling delta back to life."
"We're trying to engineer a spring flood," says Karl Flessa, a geoscientist at the University of Arizona who is leading the team that will study how the delta responds. "This is a river system that historically had a huge spring flood every year. We're trying to recreate that."
That is not all that is being done. After the pulse is over, "a small continuous flow, totalling an additional 64 billion litres, will infuse the delta over the next three years. It's a trickle compared with what used to reach the delta, but researchers still expect the water to bring around 950 hectares of the delta to life in the weeks after the pulse."