Prepare vegetables: Chop carrots and celery into 1-inch pieces. Peel and prepare small onions.

Cook vegetables: Combine carrots, celery, onions, water, and salt in a medium saucepan.

Boil vegetables: Bring to a boil, cover, and cook for 15 minutes, or until vegetables are tender.

Drain vegetables: Drain the liquid from the cooked vegetables into a 2-cup measuring cup, reserving the liquid.

Keep vegetables warm: Place the drained vegetables in a serving dish and cover to keep warm.

Prepare cheese sauce: In the same saucepan, melt margarine over medium heat.

Make a roux: Blend flour into the melted margarine to create a roux.

Combine liquids: Add the reserved vegetable liquid and enough milk to the measuring cup to make 2 cups of liquid total.

Incorporate liquid: Gradually stir the liquid mixture into the flour mixture, ensuring no lumps form.

Cook sauce: Cook over medium heat, stirring constantly, until the sauce begins to thicken.

Add cheese and Worcestershire: Stir in grated Cheddar cheese and Worcestershire sauce until the cheese is melted and the sauce is smooth and thickened.

Combine and serve: Pour the cheese sauce over the vegetables and drained salmon in the serving dish.

Serve hot over baking powder biscuits or mashed potatoes.