Add the onions, celery and carrots to the casserole. Cover and cook over low heat just until softened, about 5 minutes. Add the tomato paste and cook over moderately high heat, stirring until the paste is lightly browned, about 5 minutes. Add the wine and cook, scraping up any browned bits stuck to the pot, until nearly evaporated, about 5 minutes. Add the water, season with salt and bring to a boil. Return the lamb and any accumulated juices to the casserole. Cover and braise in the oven for about 2 1/2 hours, until tender.