As per report, for over a decade the federal government has spent nearly $700 million on habitat improvement in the Columbia River Basin.

The move aimed at improving the population of salmon and steelhead that were endangered by hydroelectric dams.

As per experts, the project so far has been the largest and most expensive habitat restoration program in the country. The program majorly has been the focus of federal management plan to repair the damages being brought by the dams to the fish.

Critics, however, said that depending heavily on habitat improvement is not sufficient for restoring wild fish runs and getting them off of the endangered species list.

The management plans include reduction of the impacts of fish that were artificially bred on the wild ones, improvement of fish passage, operational changes at the dams and keeping predators such as Caspian terns at bay.

The plan has undergone changes over the past two decades after it has been litigated in court. The latest version is now also facing legal challenges and is set for hearing on Tuesday.

Federal officials defended the plan by citing the record number of sockeye salmon, coho and chinook that returned last year, which they say can be attributed to the improved habitat.

Mining, overfishing, logging, pollution and water diversions have, however, led to the plummeting population of the salmon, said experts.

Todd True, the lawyer representing the environmental groups in the case, said, "Good habitat is beneficial, but the elephant in room is impact of the dams. Let's address it and not get distracted by the idea that we're spending millions of dollars on habitat so we must be doing something right".