Release Allocation

Overview

The objective of this section is to verify and validate the HEC-ResSim operations feature: Release Allocation. This is accomplished by creating a simple ResSim model and several operation sets with different Release Allocations. This document covers the following types of Release Allocations: Balanced, Sequential, Stepped and Release Allocation using IF BLOCKS.

Model Setup

A simple ResSim model was set up to be used for all the simulations, consisting of a single stream and one reservoir. To properly test Release Allocations, the reservoir was developed to have two controlled outlets as well as a diverted outlet. Figure 1 displays the model schematic and the physical attributes of the reservoir. For all Operation Sets, the same Zones and rules were used.

Balanced Release Allocation

Model Setup

To test Balanced Release Allocation, an Operation Set and Allocation Set were created and named Balanced_Allocation and Balanced, respectively. Figure 2 displays the Allocation Types and weights for the main dam and the diverted outlet. For this test, all outlets were set to balanced and given a weight of 1.0.

Results and Discussion

With all outlets and outlet groups set to Balanced with a weight of 1.0, the releases from the Reservoir-Dam at Stream and the Reservoir Diverted Outlet should equal each other. In addition, all outlets within the Dam Outlet group (Outlet 1 and Outlet 2) should equal each other. The Release Decision Report in Figure 3 shows that when a total release of 100 cfs is being released from the dam, the releases from Reservoir-Dam at Stream and the releases from the Reservoir Diverted Outlet are both 50 cfs. Also, when looking at how the 50 cfs is being released from the Reservoir Dam at Stream, the report shows that Outlet 1 and Outlet 2 are both releasing 25 cfs. The plot of releases can also be seen in Figure 4. This test verifies that the Balanced Release Allocation balances releases across outlet groups and within.

Sequential Release Allocation

Model Setup

To test Sequential Release Allocation, an Operation Set and Allocation Set were created and named Sequential _Allocation and Sequential, respectively. Figure 5 displays the Allocation Types and weights for the main dam and the diverted outlet. For this test, the releases were set up to first release from Reservoir-Dam at Stream first and then Reservoir-Diverted Outlet. Within the Reservoir-Dam at Stream, the outlets were set up to sequentially release from Outlet 1 and then Outlet 2.

Results and Discussion

With all outlets and outlet groups set to Sequential, the releases should cascade through the outlets in the order of Outlet 1, Outlet 2, Res_Diversion. The next outlet should not be operated until the outlet before it either reaches max capacity per rule restrictions or a physical boundary condition. The Release Decision Report in Figure 6 shows and example where releases cascade through the list based on priority and also when physical limitations can occur. Outlet 1 has the highest release and is being limited by the outlet capacity. As the releases increase, Outlet 2 releases start to increase until it also hits a physical limitation. After this, the Res_Diversion starts to release. Figure 7 shows a plot of the releases. The plot displays that Outlet 1 is the highest priority while Outlet 2 follows and is then followed by Res_Diversion. This test verifies that the Sequential Release Allocation releases from outlets according to the priority they are given.

Stepped Release Allocation

Model Setup

To test Stepped Release Allocation, an Operation Set (named Stepped_Allocation) and Allocation Set (named Stepped) were created. For this test, the Reservoir was set to Stepped with Reservoir-Dam at Stream and Reservoir-Diverted Outlet both having their Percent Release Capacity decrease as shown in Figure 8. Reservoir-Dam at Stream was also set to Stepped, with Outlet 1 and Outlet 2 both having their Percent Release Capacity decrease as shown in Figure 9.

Results and Discussion

For the Reservoir (see Figure 8 for reference), the bottom row (row 3) indicates that the total dam release, if less than or equal to 100% of the Diverted Outlet's capacity, should go to the Diverted Outlet. The middle row (row 2) indicates that if the total dam release is less than or equal to 100% of the Diverted Outlet plus 50% of the Dam at Stream, the releases to the Reservoir are intended to go to the Diverted Outlet first and then the Dam at Stream. The top row (row 1) indicates that if the total dam release is greater than the sum of the Dam at Stream and Diverted Outlet, the excess is shared by both. Looking at the Release Decision Report in Figure 10, on 08May2099 at 15:00, the total release from the dam is 100 cfs. That release is being made solely from the Diversion.

For the Dam at Stream (see Figure 9 for reference), the bottom row (row 2) indicates that the total dam release, if less than or equal to 75% of the Outlet 2's capacity plus 25% of Outlet 1's capacity, the releases to the Dam at Stream are intended to go to Outlet 2 first then Outlet 1. The top row (row 1) indicates that if the total dam release is greater than the sum of the Dam at Stream and Diverted Outlet, the excess is shared by both. Referring to the Release Decision Report in Figure 10, on 08May2099 at 16:00, the total release from the Dam at Stream is 199.75 cfs, of which 49.94 cfs (25%) is being released from Outlet 1 and 149.81 cfs (75%) is being released from Outlet 2. Figure 11 shows a plot of the release capacity settings being met. This test verifies that the Stepped Release Allocation releases from outlets according to the release capacities that are set.

Release Allocation If Block and Weights

Model Setup

To test Release Allocation using an If Block, an Operation Set and Allocation If Block were created and named IFBLOCK _Allocation and IF_B, respectively. For the If Block, two Release Allocations Sets were created named IF_Cond1 and IF_Cond2. In addition to testing If Blocks, weights were also tested in this case. Figure 12 displays the IF Block, the Allocation Sets and the weights assigned to each outlet. For this test, the If Block was set to follow IF_Cond1 if the Reservoir Pool Elevation's previous value exceeds 75 ft (HighPool) else it would follow IF_Cond2 (LowerPool). In High Pool conditions, releases would only be made from the Dam at Stream (all weights set to 1) and the Diverted Outlet would not release (weight set to 0). In Lower Pool conditions, releases would only be made from the Diverted Outlet (weight set to 1) and the Dam at Stream would not make releases (all weights set to 0).

Results and Discussion

With the If Block, releases should only be made from the Dam at Stream when the reservoir elevation exceeds 75 ft. When the reservoir elevation is less than 75 ft, releases are to only be made from the Diverted Outlet. The Release Decision Report in Figure 13 shows that the elevation exceeds 75 ft on 09May2099 at 03:00. Until 03:00, all releases are being made from the Diverted Outlet and the Dam at Stream was not making releases. At 04:00, where the previous elevation exceeded 75 ft, all releases are then being made from the Dam at Stream and no releases are being made from the Diverted Outlet. The plot of releases can also be seen in Figure 14. A marker was added to emphasize the 75 ft benchmark where the releases are to switch outlet groups. This test verifies that the Release Allocation If Blocks and Weights allow releases from outlets according to the conditions and weights given.