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SCIENCE · INVESTIGATE AND EXPLAIN

Compare reservoir allocation policies

Hold inputs fixed while comparing requested and fulfilled allocations.

Learning outcome: Account for both service and storage changes when a downstream request increases.

Starting recap

Daily order is inflow, capacity spill, prioritized release, then service.

All lessons are open directly. Your saved experiments remain when you leave and return.

Try

Regular release 5 to 10 raises actual release 35 to 70 while service falls 140 to 110 and final storage 5 to 0.

Open the experiment

Predict

Will regular service remain fully supplied if the release request doubles?

Experiment

Capture regular scenarios at release 5 and 10 and reconcile the difference using all water terms.

Allocate a bounded reservoir under stress

Fictional water-allocation policy · separate observed river record · Original fictional reservoir, capacity 100 m³ and initial storage 40 m³. Each daily bin receives all its supplied inflow, spills above capacity, prioritizes the requested downstream release, then supplies service demand from remaining water. No evaporation, groundwater, within-day hydraulics or forecast. Release targets are policy assumptions, not ecological adequacy thresholds. Unmet requests are not water fluxes. This model is not calibrated to the separate USGS river record.

Reset keeps your prediction, captures and practice history.

One reservoir, two requests and a fixed order

Regular inflow; service request 20 m³/day. This fictional store starts with 40 m³ and holds at most 100 m³. The requested controlled downstream release is 5 m³/day. The service request is 20 m³/day. These are supplied teaching conditions, not a real reservoir forecast or recommended ecological flow.

Predict before comparing: if you increase the release request under the same inflow scenario, what happens to service and storage? Treat your preferred allocation as a stated choice; the arithmetic does not decide whose needs should take priority.

  1. Receive the whole day's supplied inflow into the starting store.
  2. Spill any volume above 100 m³ before either requested allocation.
  3. Prioritize controlled downstream release, capped by the water available.
  4. Supply school/community service from the remaining water; retain the remainder for the next day.

This daily event order is a policy and timing assumption. It does not resolve within-day hydraulics. Changing the order could change spill or service. Evaporation, groundwater exchange and other losses are omitted.

Stored volume (m³): initial state and end-of-day snapshots020406080100Capacity 100 m³01234567Day 0 is initial storage; days 1–7 are after allocationLines guide the eye between snapshots; they are not within-day flow predictions.

Close the water ledger

Across seven days: 40 initial + 140 inflow = 0 spill + 35 controlled release + 140 service supplied + 5 final storage, all in m³. Balance residual: 0 m³.

Spill and controlled release both leave the store, but their timing and consequences need not be equivalent. More released water is not, by itself, evidence that ecological needs are met. Unmet requests are comparisons against a target, not additional water leaving the store.

Event order left to right; every quantity is m³ within the stated daily bin
DayStartInflowBefore spillSpillAfter spillControlled releaseAfter releaseService suppliedEndBalance residual
140206006055520350
235205505555020300
330205005054520250
425204504554020200
520204004053520150
615203503553020100
71020300305252050

Keep requests visible when water runs short

All volumes in m³; actual fulfillment plus shortfall equals the request
DayRelease requestedRelease actualRelease shortfallService requestedService suppliedUnmet service
155020200
255020200
355020200
455020200
555020200
655020200
755020200
Seven-day totals353501401400
Check a matched comparison and a timing counterexample

Worked comparison, separate from the current selection: under regular inflow, requesting 5 m³/day releases 35 m³, supplies all 140 m³ of service and leaves 5 m³. Requesting 10 m³/day releases 70 m³, supplies 110 m³ of service and leaves zero; unmet service rises to 30 m³. One reported indicator improves while another worsens. Choosing between these cases needs objectives and evidence beyond this ledger.

For the pulse case, day one begins with 40 m³ and receives 80 m³. The resulting 120 m³ exceeds capacity, so 20 m³ spills before allocations. Supplying service first would be a different timing model. Do not interpret the daily snapshot line as evidence that this pulse arrives gradually.

Transfer: keep the requested release at 5 m³/day and compare regular inflow with dry stress, then with higher service demand. Identify which input changed, show the complete water balance, and state one additional observation needed before proposing a real intervention. The separate USGS streamflow record is an observation audit; it does not calibrate these inputs or establish permitted withdrawals.

Final storage 5 m³; service supplied 140 of 140 m³ requested; unmet service 0 m³.

40 + 140 inflow = 0 spill + 35 controlled release + 140 service + 5 storage (m³). Requested controlled release 35 m³; release shortfall 0 m³. Priority and daily event order are assumptions, not a claim about the best policy.

Captures preserve recipes and replay their calculated results. They are synthetic model evidence, not physical measurements.

Understand

Compare policies under the same inputs

Start with a prediction: if requested downstream release rises from 5 to 10 m³/day, will service remain fully supplied during the regular seven-day schedule? Keep capacity, initial storage and inflow unchanged. Your comparison is meaningful because it changes one policy request while holding the supplied physical setting fixed.

The controls select a requested release and a scenario. Requested release is a target, not a promise of delivered water or an ecological minimum. In this model it has priority over service. The daily sequence is inflow, spill above capacity, controlled release, then service. Record this sequence with your prediction so that a reviewer can reproduce your reasoning.

Translate priorities into arithmetic

After inflow and spill, available water cannot exceed the 100 m³ capacity. Actual release is the smaller of requested release and available water. Supplied service is the smaller of service demand and what remains after release. Final storage is what remains after both actual outflows.

The phrase “the smaller of” is a mathematical minimum: it prevents delivering more water than exists. It does not erase the target. Release shortfall equals requested release minus actual release; unmet service equals requested service minus supplied service. These differences preserve unmet objectives while storage stays nonnegative.

For example, with 7 m³ available, a release request of 10 and service demand of 20, release receives 7, its shortfall is 3, service receives zero and unmet service is 20. That outcome expresses the chosen priority. It does not prove the priority is socially fair or ecologically appropriate.

Read matched seven-day cases

Run regular inflow with release 5 and capture the result. Initial storage 40 plus total inflow 140 gives 180 m³ available over the week. Controlled release totals 35, service totals 140 and final storage is 5, with no spill. Check 180 = 35 + 140 + 5.

Now choose release 10 while retaining the regular scenario. Capture this second recipe separately. Release totals 70, service totals 110 and final storage is zero; unmet service totals 30. The balance is 180 = 70 + 110 + 0. Daily requested service remains 20, so total requested service is still 140, not silently reduced to 110.

Write a two-column comparison. The higher request sends 35 m³ more through the controlled-release outlet, supplies 30 m³ less service and finishes with 5 m³ less storage. All three differences are needed to account for the added release. Do not attribute the full 35 solely to reduced service.

Explain what a physically feasible policy does not settle

Conservation can reject impossible water accounting. It cannot assign the relative importance of different users or decide whether a release meets downstream ecological needs. Those questions require objectives, timing, habitat information, legal context and affected communities’ evidence beyond this lab.

The USGS water-budget framework supports tracing stored water and boundary flows. It does not designate an optimal policy. Label any preference you express as a choice supported by stated priorities, then identify a measurement that could challenge its expected benefit.

Inspect at least one late-week day in each capture. A weekly total can conceal which day a shortfall first appears. The model’s daily bins can reveal that difference, but not a within-day service interruption or pressure at a tap. Avoid interpreting an orderly table as a complete engineering design.

Transfer: explain where an extra allocation came from

In another stipulated seven-day comparison, policy A releases 20, supplies 100 and finishes with 10 m³. Policy B releases 35, supplies 90 and finishes with 5 m³. Both have zero spill and identical total available water. Account for the extra release and state whether the balance identifies the better policy.

Check the reservoir-allocation transfer

Both ledgers total 130 m³. Policy B's extra 15 m³ release comes from 10 m³ less supplied service and 5 m³ less ending storage. Conservation holds, but choosing a preferred policy requires stated priorities and evidence about consequences. This is public comparison practice, not an automatic policy recommendation.

Apply

The extra 35 m3 release in this matched comparison comes from:

Public practice checks a specific claim. It does not establish independent mastery.

Separate conservation and stated policy priorities from a socially preferred allocation.

Continue

Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.

Skipping retains experiments and awards no mastery.

Previous: Draw a water-system boundaryNext: Stress-test water supply and timing
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