Carrying capacity is a relatively newer concept and at a very simplified level means comparison of the resources available as against resources consumed. The concept of carrying capacity is an expression of concern to indicate that if the rate of resources consumed is going beyond the rate at which they can be produced, then the place may face a problem of sustainability in the long term and perhaps may lead to a major collapse of the system, or even a disaster. In the case of structure plans the carrying capacity is directly proportional to the natural environmental factors and the infrastructural services and facilities provided. The first one is more important because it has a direct impact even in laying of the infrastructural facilities and services.

In planningof any sustainable town or city, the ecological and environmental aspects have a critical role to play in both the long term, as well as short term. Sustainable development is contingent upon the availability of natural as well as man-made resources and their judicious usage without much alteration and degradation on the environment in the short, as well as the long term. The dictionary meaning of the word ‘sustainable’ is ‘that can continue and/or be continued for a long time’. The technical term for this in planning is ‘Carrying Capacity’. Since we aim towards creating a sustainable community, the ecological and environmental aspects are the prime concerns and hence the ‘environmental carrying capacity’ would be the central theme of the approach for population projection of Gelephu.

Before adopting any development strategy for Gelephu it is crucially important to understand the ‘carrying capacity’ of the town specially with respect to the physical and ecological aspects. There are two main types of carrying capacities needed to be considered for population projection

 4.4.1 Physical Carrying Capacity

The physical carrying capacity defines the limit of an urban system beyond which the wear and tear would start taking place and environmental problems would follow. This limit is defined by components like habitable land and accommodation possible, water supply, slopes, power supply and space for movement which have a finite limit to the population they can support. It is measured in two dimensions, which are per space unit expressed in terms of the number of persons per square hectare of land, and per facility unit, that is, the number of occupants in a building, number of cars in the road, campers in a camp ground, and beds in a hotel. While assessing the carrying capacity of land two indicators have been taken into account, namely population holding capacity of developed land in terms of acceptable gross density and suitable land for physical expansion.

4.4.2Ecological Carrying Capacity

The ecological carrying capacity defines the degree to which the ecosystems are able to tolerate human interference without a major impact on its natural course of sustainable functioning. The immediate indicators of ecological carrying capacity are levels of air, water and noise pollution created by the settlements, some of the medium and long term indicators could be changes in the micro climate and changes in the behavior of the natural elements around the settlement.

The socio-cultural, political and economic aspects are also to be considered, but again these are linked to the natural environmental factors with respect to certain concerns. It often happens that a town may have excellent livable conditions in terms of climate and natural setting, but may not have enough water supply to sustain a large population. In that case the carrying capacity of the place would be dictated by the available resources of water. One can attempt to increase the carrying capacity by harvesting water and using it as required, but if one attempts to withdraw excessive water from the under ground sources, it may lead to a drastic fall of the water table level, and thus leading to problems of survival of the natural flora and fauna. Over a period of time this may lead to the destruction of the natural ecosystem and leading to potential disaster of drought or land slides in hilly places. Similarly it could be with the excessive creation of garbage, thus leading to an epidemic of some disease, or cutting trees and damaging water shed areas in hilly region thus inviting major landslides as well as floods in the plains at the foot hills.

Thus, while projecting the population of a town it is also very important to take into consideration carrying capacities and the related factors, including the permanent and floating populations. Carrying capacity can be enhanced through environmental awareness and action. Stopping tree cutting and mining operations in the upper water sheds will stop flooding. Using water shed management techniques will gradually correct the damage already done, enhancing the carrying capacity and future growth potential.