Road Ecology Center

Sustainable approaches to the construction and widening of roads and highways are essential to offset negative influences on aquatic habitat and fish passage in the fragile ecosystem of the Himalayan Mountains in northern India. Evidence is growing that the expanding, poorly designed network of roads and trails in mountain areas, without giving due considerations to natural processes such as geological processes and climatic severity, such as heavy monsoon precipitation, is a major cause of habitat fragmentation and degradation of both terrestrial and aquatic habitats. These effects have been quantified for aquatic primary producers (periphyton), aquatic benthic insects, and Snow Trout, a Himalayan teleost (Schizothorax richardsonii, Gray; Schizothoraichthys progastus, McClelland) that dwells in the upper Ganges River, following Indian National Highway 58 (NH-58) in the mountain region of Garhwal Himalaya, India (latitude 29 degree 61 minutes -30 degree 28 minutes N; longitude 77 degree 49 minutes -80 degree 6 minutes E). Indian Highway 58 is one of the most important highways, is 300-km long, and passes along the Alaknanda River (230 km), which is one of the parent streams of the Ganges (70 km) in the fragile mountain ecosystem of Garhwal Himalaya of northern India. Keeping in mind the heavy traffic on the highway, a RS 450 million (US $100 million) widening project was launched in 2001. The widening of Highway 58 through massive cutting of mountain slopes, the disposal of tons of the cut material downhill into the waterways in an uncontrolled manner, and the improper water management of the slopes has resulted in intensive accumulation of soil and woody debris into the aquatic ecosystem from accelerated erosion, gulling, and landslides, resulting in drastic changes in the physico-chemical and biological profile of the aquatic habitat. Detrimental effects on transparency, current velocity, conductivity, bottom-substrate composition, dissolved oxygen, periphytonic production, and the production of benthic insect communities have been documented. Feeding, spawning, and the passage of the Snow Trout cold-water fish have been degraded or destroyed. Subsequent to the widening of Highway 58, the annual gross primary production (Pg) of periphyton declined from 8771 g C m-3yr-1(96.48 k. cal m-3yr-1) to a value of 5952 g C m-3yr-1 (65.47 k cal m-3yr-1), a 32-percent decrease in aquatic habitat. The maximum biomass (standing crop) of aquatic insects declined from a mean monthly biomass of 4.926 g m-2 (February) to 1.848 g m-2, a 62-percent decrease, and a minimum monthly mean biomass of 0.408 g m-2 (August) to 0.126 g m-2, a 69-percent decrease. Subsequent to widening of the highway, the standing crop estimate of Snow Trout declined from a maximum mean monthly biomass of 2.955 g m-2 (February) to 1.201 g m-2, a 59-percent decrease, and a minimum monthly mean biomass (August) of 0.244 g m-2 to 0.082 g m-2, a 66-percent decrease. Annual productivity of Snow Trout declined from 1.309 g m-2 to 0.448 g m-2, a 66-percent decrease. This decline is believed to have been caused by increased turbidity accompanied by a decline in depth and dissolved oxygen, accumulation of fine silt and suspended solids, a decrease in primary productivity, a decrease in general benthic-aquatic insects productivity, depletion of the food supply, and loss of cover. We have recommended the following measures to restore habitat quality and connectivity of Snow Trout: • Stream restoration and stream bank stabilization using these structures: - Toe walls - Retaining walls - Stone layers - Stone arches - Terraces • Bioengineering methods by - Planting fast-growing plant species in combination with wire netting, gravel mining, and dredging in the impacted sites - Protecting riparian vegetation - Monitoring of water quality - Enhancement of fish food reserves - Sustainable approaches to road construction and widening - Proper drainage of water-saturated mountain slopes and spring runoff during monsoon season (July-August) - Sealing of side drains against underground water penetration alongside endangered sections of the highway - Construction of check dams for protection of steep gullies and side erosion of the river bed We also recommend establishment of a strong partnership among experienced, expert • Geologists • Civil engineers • Structural engineers • Environmental biologists