Nature-hungry residents in the Washington area were offered two more places to indulge their appetites yesterday as political leaders in Montgomery and Howard counties officially opened a pair of regional parks in time for the recreation-heavy summer months.

By late afternoon, about 1,000 hikers, bicyclists, boaters and picnickers had flocked to the banks of 505-acre Little Seneca Lake, the sapphire-colored centerpiece of Black Hill Regional Park in northwest Montgomery County.

In northeast Howard County, the turnout was a lot lighter at an invitation-only, lakeside ceremony dedicating the 325-acre Centennial Park, which was opened to the public in early April. But roughly a dozen families who showed up with fishing poles, Frisbees and fast food lunches yesterday morning were offered the added amusements of the Army Jazz Ambassadors and a balloon tossing contest between the county executive's staff and members of the County Council.

Danny Bowyer and his son, Karl, arrived at 8:30 a.m. yesterday to fish for bluegill and bass, using live cicadas for bait.

"I was born and raised in the country, and I don't like the city much," said the West Virginia native, who has lived the past 22 years in Baltimore. "I feel comfortable in a place like this. I really do."

Although the parks are roughly 25 miles apart and operated by different government agencies, their histories -- each was years in the making -- reveal the complex and lengthy process required to preserve open spaces, particularly in areas where new residential and commercial developments are changing the landscapes every day.

In the case of Centennial Park, 22 years have passed since a 12-member board appointed to advise county officials on the use of parks and wetlands first recommended its site and began purchasing the land.

Although it has been fewer than 10 years since members of the Maryland-National Park and Planning Commission decided to consolidate two stream valleys into a regional park, board chairman Norman Christeller said yesterday that some land included in Black Hill was acquired as early as 1966.

Both the Howard Recreation and Parks Department and the Park and Planning Commission, which serves Montgomery and Prince George's counties, use state and local funds to buy land for parks.

But acquiring enough to make up a park is a time-consuming process that involves haggling with property owners over prices and, in some cases, waiting until land is donated to keep down the price of a park.

Centennial Park cost Howard County $11.8 million, a figure officials said would be difficult to duplicate today.

At $28.5 million, Black Hill, which will encompass more than 1,900 acres when it is completed in a few years, is a bargain, Christeller said.

Because regional parks are generally in environmentally sensitive areas, they must pass a rigid review process to ensure that local governments, in their rush to preserve nature, are not destroying it.

"Creating a park is not just a matter of filling a hole with water, throwing up a couple of ball fields and selling hot dogs," said Howard G. Crist Jr., who headed the board that created Howard's first general plan for parks. "Even with a community park, you have to compete for the land and make sure you don't make anybody angry in the process. These things are supposed to last a lifetime."

Although these two parks are currently open and in use, the importance of preserving park land has never been more apparent, those involved with the projects said.

In the 60 years since the Maryland-National Park and Planing Commission was created, Christeller said, Montgomery County has changed from a summer retreat for Washingtonians into a self-supporting metropolitan area.

"As that urbanization goes on, the need for green space and a park system that provides people with places they can go for casual recreation becomes more important," Christeller said. "Along with our schools, the park system is the most frequently mentioned reason why businesses establish a corporate or regional headquarters here."

Centennial Park, set against fields of wildflowers and framed by a heavy fringe of tall grasses and oak trees, is the first of five regional parks planned for the still heavily rural county. By the year 2000, county officials hope to have set aside another 2,000 to 3,000 acres of open space, bringing the total to 6,000 acres, or 35 acres for every 1,000 people.

Montgomery will have about 27,000 acres of parks when its six-year, capital improvement program is executed, while Prince George's will have about 16,000 acres.

At the dedication of Centennial Lake, the Rev. Lyle Buck enumerated the personal joys to be had in the park, which, he said, will provide "freedom from the enslavement of walls, plastics and electronics.

"From the swans on the lake to the ants on the picnic lunch, from the hiker's view of rabbits to the home run slugger, from the hungry and leaping fish to the paddleboats, may this park be just right for the people of Howard County."