The Confluence Water Resources Planning Model

Future climate change is expected to result in many serious challenges, not the least of which is its uncertain effect on future water supplies and demand.

Sound water resources planning must systematically consider how well potential resource strategies perform in light of the risks associated with changes in climate.

Confluence has been upgraded to accurately assess these risks.

Confluence and Climate Change

The fact is that we don't know how climate will change in the future, and the impacts on water supplies and customer demands of changes in climate are even less predictable. In order to understand the robustness of alternative resource strategies, it is important to test them against a range of climate change scenarios. Confluence has been upgraded to enable users to easily do this by specifying the impacts of each climate change scenario on water supply and demand.  

Supply. Confluence users can define sets of monthly factors as multipliers of baseline historical streamflows. Through a simple grid structure, these sets of factors can be varied by:

• Hydrologic Year.  The manner in which flows change for wet, average, and dry years can differ.

• Source.  The flows for different watersheds and/or diversion points may be affected differently.

• Time.  Recognizing that climate change impacts are expected to grow in the future, the flow adjustments can likewise change over time.
  

Demand. Climate change can affect water demands in two ways. First, per-customer demands can change due to modified temperature and rainfall patterns. Second, population growth forecasts can be modified as a result of altered migration patterns.

• Confluence users can capture the per-customer demand impact by adjusting historical temperature and precipitation, or directly adjusting historical demands, by month, for different year types (e.g. dry, average, wet or hot, average, cool).

• Altered patterns of migration into and out of the region are handled by applying a set of annual adjustment factors to baseline population growth.
  

These added model capabilities enable Confluence users to easily and accurately compare the performance of strategy alternatives under different climate change forecasts. This will be illustrated in the Resource Strategies page.

SAMPLE CLIMATE CHANGE GRID STRUCTURE

Confluence allows specification of different impacts on streamflow for each stream and hydrologic year. It also allows definition of weather-year-specific impacts on temperature and precipitation. Moreover, these impacts can change through the forecast period to reflect increasing climate change impacts over time.

This flexibility is achieved through a three-step process.

1. The entries in each cell of the grid to the right point to series of monthly distributions. Thus, in a 1970 weather year, daily temperature would be changed according to the monthly adders contained in the series Temp_Norm. 

2. The second grid defines each of these series.  Beginning in 2015, the series Temp_Norm adds to historical daily temperature the number of degrees (F) contained in the monthly distribution T_1. In 2020, the adders change to T_2, and in 2025 to T_3.

3. The final grid shows the monthly distributions. Thus, T_1 adds one degree F to each day's temperature in May-October, and T_2, T_3, and T_4 add respectively 1.5, 2, and 3 degrees in the same months, while leaving daily temperature in the remaining months unchanged.

You can use as much or as little of this flexibility as you wish in defining climate change scenarios. So you can specify and compare climate change impacts of any degree of complexity.

NEXT:  Resource Strategy Alternatives

Home 
Key Features
Base Case Set-Up
Base Case Results
Climate Change
Resource Strategies
Download Trial Version
About Us
Contact Us