Namzi Mwafi, 23, has one job, day in and day out: find water for his family.

Dozens of his extended family members are sheltering together in a two-bedroom apartment in Rafah, a city in southern Gaza near the territory’s border with Egypt, he says. The oldest, his grandmother, is 68; the youngest, a cousin, is 6 months old.

To keep them alive, Mr. Mwafi says he wakes up at 4 a.m., spending hours waiting for water at a crowded filling station. Sometimes, he has to fight to keep his place in line and sometimes there is nothing left when his turn comes.

When he is lucky, he pushes his heavy trolley home through the sand and the family rations the haul to about a glass a day each.

There is practically no gas or other fuel left in Gaza, according to the United Nations agencies operating there, so some people are building makeshift clay or metal ovens to cook. Firewood and coal have also largely run out, so families are burning stripped-down doors, shutters and window frames, cardboard and grasses. Some simply do not cook, eating raw onions and eggplants instead.