as a Planning Unit for Sustainable Land Management in the
Engr. Santiago R. Baconguis
A watershed is any sloping surface that sheds water. It implies a body of land bounded above by a topographic divide and below by the level at which water drains from. Watershed function by receiving input water from rainfall, storing and releasing it according to the three basic attributes of water: quantity, quality and timing.
The watershed is used as the main biophysical resource to integrate the concerns of productivity, equity and ecological balance. As the key-planning unit, it possesses well-defined boundaries and interactive relationships for biophysical analysis. In addition, it can also be disaggregated into mini- and micro-watershed units allowing the integration of production performance with soil and water conservation measures. It can also be readily linked to the broader or higher levels of management whether at regional, provincial or municipal level.
The sustainable land management activities uses the watershed as a planning unit due to the following reasons: (1) Upland-Lowland-Coastal Interaction. It clearly illustrates the relationship between the uplands, lowlands and the coastal zones. Development/degradation in the uplands will impact the lowlands and coastal areas; (2) Complementary Uses. Watersheds possess inherent multiple uses whose location and choice of uses within a shared environment must be examined for their complementation. The hierarchy of watershed units provides the element of continuity that facilitates the analysis of cause and effects of land use changes in the watershed, and (3) Water as Integrator. The watershed is an ecosystem with its own unique set of physical, biological and human components that are constantly interacting and dynamically changing. Water attributes as a product of the watershed, is an excellent indicator of this interaction/change.