Water stress & water salience: implications for water supply planning

Figures & data

Figure 1. (a) Case location; (b) organizational hierarchy (SNWA = Southern Nevada Water Authority; LVVWD = Las Vegas Valley Water District); and (c) Lake Mead operational rule diagram

Figure 2. Case data: (a) monthly per capita water use in the LVVWD services area; (b) monthly Lake Mead water levels; (c) annual LVVWD cumulative banked groundwater volume (excluding AZ bank); (d) monthly percentage of media articles in the Las Vegas Review Journal on water issues

Table 1. Data sources and characteristics

Variable	Frequency	Source	Units
Total Water Usage	Monthly	Las Vegas Valley Water District	Million Gallons
Surface Water Withdrawals	Monthly	US Bureau of Reclamation	Acre-Feet
Groundwater Pumping	Monthly	Nevada Division of Water Resources	Million Gallons
Banked Groundwater	Annual	Nevada Division of Water Resources, Southern Nevada Water Authority, Arizona Water Banking Authority	Million Gallons
Lake Powell Elevation	Monthly	US Bureau of Reclamation	Feet
Lake Mead Elevation	Monthly	US Bureau of Reclamation	Feet
Evaporation Loss from Lake Powell	Monthly	US Bureau of Reclamation	Feet
Evaporation Loss from Lake Mead	Monthly	US Bureau of Reclamation	Feet
LVVWD Population	Annual	Clark County	Persons
Tiered Water Rates	Monthly	Las Vegas Valley Water District	$/3790 L
Media Coverage	Monthly	Las Vegas Review-Journal	Normalized % of articles on water
Mean Temperature	Monthly	National Oceanic and Atmospheric Administration	°C

Figure 3. Project methodology

Table 2. Parameter ranges and optimal values

	α	rF	u	b	σ
Lower bound	0.010	1.500	0.010	0.050	0.001
Upper bound	1.000	2.000	0.950	0.950	1.000
Optimal	0.058	1.855	0.756	0.647	0.460

Figure 4. Streamflow and population scenarios: (a) LOESS and standard error of sampled streamflow generated from downscale GCM projections and resampled observed streamflow using the index sequential method; (b) high and growth population scenarios

Table 3. Salience function performance statistics

Calibration statistics
Salience Equation	RMSE	% Bias	Corr.
f(Threshold distance)	0.002	57.5	0.812
f(Water supply volume change)	0.003	9.7	0.234
Validation statistics
Salience Equation	RMSE	% Bias	Corr.
f(Threshold distance)	0.002	17.0	0.809
f(Water supply volume change)	0.002	−67.6	0.400

Figure 5. (a) Threshold-based water salience; (b) supply change-based water salience

Table 4. Model parameterization performance statistics

Calibration statistics
Variable	RMSE	% Bias	rNSE	Corr.
Demand	33.7	3.7	0.704	0.917
Lake Mead elevation	11.00	0.3	0.927	0.969
Water salience	0.024	856	NaN	0.517
Banked groundwater	15768	3.7	0.867	0.930
Validation statistics
Variable	RMSE	% Bias	rNSE	Corr.
Demand	33.1	2.7	0.761	0.919
Lake Mead elevation	13.57	0.1	0.886	0.950
Water salience	0.055	2711	NaN	0.753
Banked groundwater	21,698	6.8	0.754	0.915

Figure 6. Observed and modeled (a) per capita water usage, (b) Lake Mead elevations, (c) water salience, and (d) banked groundwater from the chosen parameter set

Figure 7. CDF of reliability for the BAU case for (a) the exogenous water use model, and (b) the endogenous water use model

Figure 8. CDF of reliability for the response cases for (a) the exogenous water use model, and (b) the endogenous water use model

Figure 9. Heat map illustrating the evolution of water stress over time across many model runs using the high population growth and downscaled projected streamflow for the following: (a) BAU with the exogenous model; (b) desalination construction with the exogenous model; (c) BAU with the endogenous model; and (d) demand- and supply-side responses with the endogenous model