Advantages of a Market-based Approach to Conjunctive Management in the Humboldt River Basin, Nevada, USA

Andrew Aryes and Michael Taylor

ABSTRACT
In basins with a hydrologic connection between groundwater pumping and stream flow, it can be valuable to jointly, or conjunctively, manage groundwater and surface water. Nevada, like many other states, is currently revising its water management approaches and policies to support the implementation of conjunctive management. Nevada’s efforts are focused on the Humboldt River, where groundwater-pumping-induced losses in surface flows have resulted in legal action and where the State is currently leading a stakeholder-involved process to develop a strategy for conjunctive management. This article advocates for a market-based approach to conjunctive management in the Humboldt River Basin. The proposed market-based approach would require groundwater extractors to obtain “offsets” that introduce a volume of water into the river during the irrigation season equivalent to the amount their pumping is estimated to capture. Groundwater pumpers holding offsets could pump their full duty each year without imposing an external cost on downstream surface water right holders through reduced streamflow. We argue that this approach (i) aligns with Nevada water law, including prior appropriations and the Humboldt Decree, (ii) protects the rights of senior surface water users, and (iii) minimizes the negative economic consequences of restricting groundwater extraction in the basin. This article is a commentary paper focused on the potential advantages of a market-based approach and issues related to its implementation in the Humboldt River Basin; further quantitative analysis is necessary to determine the merits of this approach relative to other viable alternatives.

Keywords: groundwater, surface water, conjunctive management, water rights, water markets, offsets
Authors: ANDREW B. AYRES, Department of Economics, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557 (andrew.ayres@unr.edu); MICHAEL H. TAYLOR, Department of Economics, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557 (taylor@unr.edu)
Citation: Ayres, Andrew B. and Taylor, Michael H., 2024, Advantages of a Market-based Approach to Conjunctive Management in the Humboldt River Basin, Nevada, USA. Journal of the Nevada Water Resources Association, Winter 2024, p. 4-17. DOI: 10.22542/jnwra/2024/1/1.
DOI: 10.22542/jnwra/2024/1/1.

Potential recharge for groundwater-flow models in north-central Nevada

Keith Halford and Erica Gallegos

ABSTRACT
A potential precipitation-recharge distribution was estimated across 23 hydrographic areas (HAs) to constrain water balances of groundwater-flow models in north-central Nevada that are operated by Nevada Gold Mines. This recharge distribution was estimated from the annual 1991–2020 PRISM precipitation distribution. Precipitation volumes were reduced to representative published recharge volumes using the Maxey-Eakin method, where recharge efficiencies varied as a function of elevation, latitude, and longitude instead of precipitation rates. Estimated potential recharge agreed with the conceptual model, where potential recharge primarily occurs in mountains. In Nevada, potential precipitation recharge commonly occurs over low-permeability rocks in mountain blocks, and this study illustrates how to estimate an in-place recharge distribution for this condition, with an example from the Carlin Trend model.
Authors: KEITH J. HALFORD, Halford Hydrology LLC, 1000 W. Robinson St., Carson City, NV 89703 (khalford@halfordhydrology.com); ERICA R. GALLEGOS, Nevada Gold Mines, 1655 Mountain City Hwy Elko, Nevada 89801, (egallegos@nevadagoldmines.com)
Citation: Halford, Keith J. and Gallegos, Erica R. 2024, Potential recharge for groundwater-flow models in north-central Nevada. Journal of the Nevada Water Resources Association, Winter 2024, p. 18-42.
DOI: 10.22542/jnwra/2024/1/2

Trends in flow of the Humboldt River, North-Central Nevada, 1945 to 2020

David Prudic
ABSTRACT
The Humboldt River flows from its headwater areas east of Elko to the Humboldt Sink southwest of Lovelock. Water in the river is used primarily for irrigation of crops and the river has been fully appropriated and adjudicated since the 1930’s. Groundwater pumping for irrigation began increasing in the 1960’s. Dewatering of mines began in the early 1990’s. Pumping of groundwater has raised concerns over its effects on flow in the river, particularly during periods of drought. Five continuously operated gaging stations on the Humboldt River were used to evaluate if groundwater pumping since the 1960’s could be causing a decrease in flow.  

Various analysis using annual, monthly, and daily flows at Humboldt River gaging stations indicate flow between the Comus and Imlay gaging stations showed an increase in loss that exceeded estimated measurement errors. The mean difference in flow between gaging stations during two droughts—water years (WYs) 1953 to 1955 and 2012 to 2015 also indicate increased loss between the two gaging stations. Daily mean flows at the gaging stations show little difference between October 1945 to September 1969 and January 2007 to September 2020 except for the Imlay gaging station where the daily mean flow for the latter period was less 90 percent of the time than the earlier period. The lack of a change in flow at the Comus gaging station is consistent with the number of days when daily mean flow at the gaging station was less than 1 cubic foot per second (cfs) for two 13-year periods with nearly the same mean flow (1,297 days during WYs 1951 to 1964 and 1,291 days during WYs 2007 to 2020). However, the number of days when the daily mean flow at the Imlay gaging station was less than 1 cfs increased from 64 days during the earlier period to 941 days during the later period. In conclusion, flow at gaging stations upstream of Comus indicates no measurable decrease that could be attributed to groundwater pumping, whereas a measurable decrease in flow at the Imlay gaging station is best explained by groundwater pumping near the river downstream of Comus.
Authors: DAVID E. PRUDIC, 702 Crain Street, Carson City, NV 89703 (davideprudic@gmail.com)
Citation: Prudic, David E. 2024, Trends in flow of the Humboldt River, North-Central Nevada, 1945 to 2020. Journal of the Nevada Water Resources Association, Winter 2024, p. 43-64.
DOI: 10.22542/jnwra/2024/1/3.