Before Yuen Long New Town was developed, agriculture thrived in the area. In the 1950s, Yuen Long and Tuen Mun constituted the largest agriculture area in Hong Kong. The open and fertile Yuen Long Plain, with easily accessible water for irrigation, was ideal for rice cultivation. 90% of the farmland to the south of Castle Peak Road in Yuen Long was paddies. Along Castle Peak Road, where there was convenient transportation, some farmers switched to growing vegetables that could be sold at higher prices. In the 1960s and 70s, livestock farming boomed on the Yuen Long Plain, due to improved transportation and the abundant land and water.

In the 1970s, many paddies in Yuen Long were converted to vegetable farms or fishponds. Until the 1990s, agriculture of the Yuen Long Plain was dominated by fishponds, orchards and garden plants, with some leisure farms cultivating fruits for visitors to pick.

Back in the Jiajing Reign of the Ming Dynasty, the section of Shan Pui River near today’s Tai Shu Ha Tin Hau Temple at Tai Kei Leng was deep enough for navigation by ships. A local market, called Tai Kiu Tun Hui and later Yuen Long Hui, was also established. The blooming market in turn attracted people to cultivate the nearby land, and eventually Shap Pat Heung took shape. But the market was abandoned during the coastal evacuation. After the evacuation was lifted, large ships could no longer navigate the channel as it was silted up. In the eighth year of the Kangxi Reign, the market was relocated to the north of Yuen Long Chung (also named Shui Mun Tau), which is today’s Yuen Long Kau Hui (Old Market).

In the beginning of the 20th century, land transport gradually replaced navigation by river channel, as Castle Peak Road was connected to the south of Yuen Long Kau Hui, and Yuen Long Chung became increasingly shallow. In 1915, Sun Hui (New Market) was established on the opposite side of Yuen Long Chung. By the 1930s, this became the largest market in the New Territories. Today, there is basically no waterways travel, for either goods or passengers. The new market was demolished in the 1980s. The old market remains, but is no longer active.

The estuary is a rich fishery ground. Apart from using fishing boats, fishermen would set up stake nets on the mudflat of Shan Pui River estuary to catch fish. However, the most important activity of Deep Bay was fishpond culture. Near the end of the 1950s, many paddy fields were converted to gei wais and fishponds. In the 1960s, more gei wais became fishponds, transforming Yuen Long into the largest fishpond area in Hong Kong.

Gei wais are connected to the river in various ways. But when gei wais are turned into fishponds, they are disconnected from the river. In summer, when evaporation rates are high and water levels of fishponds falls, fishermen would pump river water into the fishponds. After the 1970s, however, Shan Pui River was contaminated, and the water could no longer be used to rear fish in fishponds.

The Deep Bay mangroves and wetlands in the lower course of Shan Pui River attract large flocks of birds, particularly resident and migratory waterbirds. In the 1970s, there was active hunting of ducks and waders. Today, hunting is banned by law.

In the past, besides the waterway connecting Yuen Long and other places via Shan Pui River and Deep Bay, there were several major land routes for transporting goods and firewood. After the establishment of country parks, these ancient trails become hiking trails.

After the Second World War, during the 1950s and 1960s, fuels were in short supply in Hong Kong. There was extensive felling of local forests for firewood. Later, the government began plantations. In 1979, the region around the upper course of Shan Pui River was delineated as Tai Lam Country Park, to offer the public a place for leisure, education, conservation and research. The Agriculture, Fishery and Conservation Department established Yuen Tsuen Ancient Trail and Tai Lam Education Trail, enabling people to explore the upstream landscape and ecology. Streams in the area also attract many hikers. In addition, a volunteer group has established holiday village for visitors.

Since the 1960s, Hong Kong’s population has boomed, and the foundation for urbanising Yuen Long was laid, as flood control works and roads along the river connecting the market and various villages of Shan Pui River basin were in place. In 1973, the government implemented the new town development scheme, to disperse the urban population. In 1978, Yuen Long became a new town, and its population increased to 87,000. Farmland was turned into high rises and streets. Wang Chau Industrial Estate (since renamed Wang Chau Industrial Park), the second largest industrial estate in Hong Kong, was established to the north of Yuen Long New Town.

Due to the dense population in Yuen Long New Town, and flourishing industrial and commercial activities, water in the lower course is basically wastewater, and cannot be used for drinking or irrigation.