Delta Watershed Model

Delta Watershed Model

A major highway project, the South Fraser Perimeter Road passes through the low lands of the Corporation of Delta, British Columbia (BC); crosses agricultural areas; and runs adjacent to the boundary of the environmentally sensitive Burns Bog. The SFPR drainage system needed to be an integral part of the Delta’s drainage and irrigation system. The analysis of the complex inland water system with tidal influence at the outfalls to the Fraser River and the Pacific Ocean required a comprehensive modelling approach that properly simulates the performance of the system in both drainage and irrigation mode operations, as well as considers the impact of the unique hydrology of the Burns Bog on the surrounding drainage system.

Burns Bog’s hydrology was assessed by the Burns Bog Water Balance Model (BBWBM) using the US Army Corps of Engineers’ two‑dimensional Gridded Surface Subsurface Hydrologic Analysis Model. The primary objective of the BBWBM was to simulate the outflows at the perimeter of Burns Bog during critical hydrologic events, as well as through the various seasons of the year. The BBWBM model provided input to the Delta Watershed Model (DWSM).

The DWSM was built on the XPSWMM model platform by XP Solutions and was used to assess the hydrology and hydraulic performance of the Delta drainage and irrigation system on the 13,000-hectare (ha) watershed. The DWSM incorporates over 430 kilometres (km) of Delta’s ditch network, 1,700 culverts and bridges, 21 tidally influenced outfalls, 23 pump stations, 4 automated water level control gates, and some 200 other control structures. It also includes Real-Time Control (RTC) features for controlling pumps and gates from water surface elevations at remote locations.

Initially, the DWSM in drainage mode configuration was used for evaluating potential SFPR impacts and supporting the design of the SFPR drainage system. Later, the DWSM in irrigation mode configuration was used to support the design of the Delta Irrigation Enhancement Project (DIEP). The latest configuration of the DWSM incorporates the Cougar Creek and Northeast Interceptor Canal Watershed at the eastern boundary of the Delta low lands. Currently, the model is used for evaluating the impacts and supporting the design of drainage systems for various projects on the watershed in the context of Delta’s overall drainage and irrigation system’s performance.

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