Okanagan Basin Research Articles

Age Determination of Rocky Mountain Ridged Mussels (Gonidea angulata) in the Okanagan Basin, Canada

Age Determination of Rocky Mountain Ridged Mussels (Gonidea angulata) in the Okanagan Basin, Canada

Testing and applying baseflow approaches to environmental flow needs

Environmental flow need (EFN) is defined as the quantity, quality, and timing of flow that are required to maintain the health of riverine ecosystems and human and societal sustainable development. Numerous research frameworks have been developed and used with a range of sophistication, data requirements, and management strategies. Recently, 90% of the monthly baseflow derived from groundwater has been proposed as the presumptive standard for the groundwater contribution of EFN. However, this proposed groundwater presumptive standard has not been compared to the field-based EFN, which limited its practical application in water management. Therefore, we ask whether baseflow can be used as an index of EFN, and if so, is 90% of monthly baseflow robust for aquatic ecosystems? We selected nine watersheds in the Okanagan Basin (Canada) with well-established EFN based on extensive fieldwork and local experts' knowledge to address this research question. Four baseflow separation methods were adopted to derive the long-term monthly baseflow. We then compared the baseflow against field-based EFN and found that different ranges of baseflow can represent field-based EFN. Specifically, 86%-159%, 93%-151%, and 128%-139% of monthly baseflow can be used as EFN standards for snow-melting, summer, and fall-winter, respectively. Further, we found that 102%-150% of the monthly baseflow should be maintained, implying that the presumptive standard underestimated EFN in our study region. Finally, we recommended that baseflow can be an effective index for EFN; however, watershed management should recognize local aquatic conditions in applying the baseflow EFN index for conjunctive watershed management.

Infestation and timing of use of non-crop plants by Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) in the Okanagan Basin, Canada

AbstractDrosophila suzukii (Matsumura) (Diptera: Drosophilidae), was first detected in 2009 in the Okanagan Basin, British Columbia, Canada. During 2010–2016, 94 570 fruits of 35 non-crop species, from 12 plant families, were collected from 101 sites where adult D. suzukii flies were trapped, and incubated in a controlled environment. In total, 450 adult D. suzukii emerged from 62 of 929 fruit collections, and from 10 host plant species in five families, of which six species are native to the region. Five plant species are reported for the first time as hosts of D. suzukii, and 11 species for the first time as non-hosts. Measures of fly occurrence and infestation reveal it to be relatively abundant in five hosts and low in others. The fly reproduced in a succession of host plants, with first infestation of each from mid-July through mid-September, and was present until mid-October, but overwintering stages were not found. Degree-day accumulations for the infested period suggest that three to five generations of D. suzukii developed on non-crop plants and formed a large contribution to the annual increases observed in trap counts in a semi-arid cold winter climate, with implications for many strategies of pest management.

Coupling stated preferences with a hydrological water resource model to inform water policies for residential areas in the Okanagan Basin, Canada

To improve the behavioural realism of a water resource model, this study coupled hydrologic modelling with stated preference research, thereby incorporating an empirical estimate of behavioural parameters to represent residents’ landscape decisions in an urban environment. The stated preference data came from a discrete choice experiment in which residents were asked to choose among several possible lawn plots — varying in size, turf variety, and aesthetic qualities. The discrete choice experiment also included subsidies for lawn replacement, and information about estimated water use and watering costs for each lawn choice. We prepared a behavioural model utilizing coefficients from a mixed logit model estimated from the stated preference data, and then coupled it with a water resources model of the Okanagan Basin using the Water Evaluation and Planning System. We then conducted a scenario analysis using the coupled socio-hydrological model to simulate the extent to which residents would adopt alternative lawns under varying incentives and subsequently computed corresponding changes in water demand. The results indicate that proposing alternative lawn configurations to residents and providing site-specific information about the potential for reduced watering costs, along with a small subsidy, could lead to considerable reduction of outdoor water use through voluntary adoption. Under a scenario in which the attributes of the suggested lawn configuration matched those most preferred by residents in the choice experiment, the suggested configuration was widely adopted in the Okanagan, but a scenario with a more extreme water conserving lawn configuration reduced overall outdoor water use by a greater amount even though the configuration was adopted by a smaller percentage of residents. This study illustrates the relationship between lawn preferences and water use and supports calls to integrate hydrological and social modelling in order to capture the complex interactions between human behaviour and water use.

Managing Drought Risk in the Okanagan: A Role for Dry-Year Option Contracts?

Although markets have proven effective at moving scarce water to high-value uses, the potential economic efficiency gains are often insufficient to convince water users to accept more market-oriented water allocation mechanisms. Water users in the semi-arid areas of British Columbia, including the Okanagan basin, are deeply concerned about the potential negative impacts of water markets. With drought risk rather than chronic water scarcity as the primary water management challenge, water users' concerns are reasonable. Dry-year option contracts may capture some of the benefits of market-based instruments without the risk implications of conventional water markets. Dry-year water option contracts are financial instruments that water-sensitive users can use to hedge themselves against drought impacts, and if appropriately managed through a water supplier, they may be an efficiency-enhancing alternative to crop insurance. We argue that with appropriate support, dry-year option contracts can be a useful low-cost tool to mitigate drought impacts in semi-arid regions of British Columbia. Such contracts may enable the innovative local water management solutions envisioned in British Columbia's recently enacted Water Sustainability Act.

Profiling Farmers’ Preferences about Drought Response Policies Using a Choice Experiment in the Okanagan Basin, Canada

Farmers can play a crucial role in water management during water shortages, yet little is known concerning the preferences of farmers for various options in drought response planning. In this paper we demonstrate the use of a discrete choice experiment to investigate the preferences of farmers about options for drought response policies in the Okanagan region of British Columbia, Canada. In the choice experiment, three policy instruments were varied across possible drought response plans: mandatory reductions in water supply, reallocation of entitlements to available water, and opportunities for water trading. Results show that participating farmers, as a whole, were more likely to accept drought response plans with moderate levels of mandatory water reductions, water allocations according to the sensitivity of crops to water loss, and opportunities for water trading between farmers. When analyzed according to the primary crop cultivated, grape growers were more likely to prefer drought response plans with opportunities for water trading between all water users, whereas ranchers were more likely to prefer drought response plans that feature high levels of mandatory water reductions. We contrast our findings with preconceptions about farmers’ preferences concerning water use policies. We also discuss broader implications of the research, including the usefulness of choice experiments for informing the development of effective drought response policies.

Integrated water resource management and British Columbia’s Okanagan Basin Water Board

This study examines successes and limitations of integrated water resource management (IWRM) for the Okanagan Basin Water Board (OBWB), a basin management entity in British Columbia, Canada. Effective governance, adequate financing and scientifically informed decision making are attributes contributing to the OBWB’s IWRM success. OBWB’s IWRM challenges include meaningful engagement of First Nations, public apathy towards water governance, succession planning for retiring professionals, and management authority limitations. Constraints on the OBWB’s authority and perceived lack of need to formalize the IWRM approach will affect other local IWRM applications. The study adds a western Canadian example of basin management to IWRM practice.

Intra-utility performance management model (In-UPM) for the sustainability of small to medium sized water utilities: Conceptualization to development

Small to medium sized water utilities face serious challenges to meet broad sustainability objectives, because of technical, human and financial constraints and limited involvement in the inter-utility benchmarking. Most of these utilities are unable to address the performance gaps for various functional components, such as personnel, operational, financial, etc., of their water supply systems and rely on emergency response. Even if the information obtained from such benchmarking process is available, the outcome (indices) showing performance of these components, at the utility level, is useful for top level management. The operations management is more interested in the performance of sub-components (under each functional component) of the water supply systems within the utility. An intra-utility performance management model is conceptualized and developed for effective decision making at both the levels. A hierarchical based top-down approach initiates from overall sustainability objectives at the top, followed by primary and secondary performance measures of the sub-components, and indicators (basic building blocks) receive inputs from data/decision variables at the bottom. The model assesses the performance of each component and sub-component as ‘high’, ‘medium’, or ‘low’. Fuzzy based technique has been employed to deal with uncertainty issues due to data limitations and vagueness in expert knowledge. Sensitivity analysis helped to rank the indicators for their contribution in decision making. The model is implemented for a medium sized utility containing three sub-systems in the Okanagan Basin (BC, Canada). The results demonstrate the model's practicality to efficiently achieve sustainable performance in small to medium sized water utilities.

Risk-Based Framework for Improving Customer Satisfaction through System Reliability in Small-Sized to Medium-Sized Water Utilities

AbstractSmall-sized to medium-sized water utilities (SMWU) face severe challenges to maximize the customer satisfaction (CS) because of operational failures, limited trained staff, and financial issues. Conventional methods are based on performance benchmarking and interviews, which might not be feasible at all times for SMWU. A novel risk-based framework is developed for improving CS by improving the reliability of water supply systems operating in a utility. The framework is primarily based on comprehensive analysis of customer complaints and staff’s observations on related complaints. Customer dissatisfaction is evaluated in terms of risk of not meeting CS, which starts when a customer reports a complaint; however, a complete evaluation of CS depends on the duration between the time of the report and the response until the complaints’ full resolution. Different categories of complaints are identified from an exhaustive record of a medium-sized utility in Okanagan Basin (British Columbia, Canada). For r...

A decision support system for improving “fish friendly” flow compliance in the regulated Okanagan Lake and River System of British Columbia

The Okanagan Valley of British Columbia (BC) has one of the lowest per-capita water supplies in Canada. Large fluctuations in water supplies routinely induce seasonal extremes of flood and drought conditions that challenge the ability of decision makers to operate complex water management infrastructure (dams, dikes, irrigation networks, flood control channels) to satisfy competing objectives to meet human-system versus natural-system needs (e.g. protect property, irrigate land, protect aquatic biota). An audit of water management performance from 1982 to 1997 indicated frequent non-compliance of water regulation decisions with “fish friendly,” lake level and river discharge ranges specified by the 1982 Canada–BC Okanagan Basin Implementation Agreement (OBIA). Development and deployment of an environmental decision support system (EDSS) to provide real-time fish and water management tools (FWMT) to decision makers offered a potential means to improve the balance of water management decisions affecting both human and natural systems. The resultant FWMT-EDSS described here includes: a coupled set of four biophysical models of critical relationships among climate, fish and water that interact with a fifth water management rules model used to predict potential consequences of decisions for fish and other water users; a network of stations providing nearly instantaneous observations of lake elevation, river-discharge, precipitation and snowpack; a Structured Query Language (SQL) server database; an internet-accessible, graphical user interface; and a set of end users representing decision makers from government agencies, industry and local communities. FWMT provides a risk assessment framework to integrate biophysical processes, deal with multiple species and geographic locations, anticipate socioeconomic outcomes of water management decisions and increase cooperation among water users to improve fish and water management. Comparisons of observations from pre-FWMT “control” versus FWMT deployment years (n = 20 and 11, respectively) indicate significant improvements at both daily (p < 0.001) and annual (p < 0.05) time scales in compliance of water management decisions with OBIA guidelines to protect salmon during critical egg-to-fry emergence stages. These FWMT-enabled improvements were achieved without any increased damage to water system infrastructure, riparian property or agricultural production from flood or drought conditions.

Modeling coupled surface water – Groundwater processes in a small mountainous headwater catchment

Summary Hydrological models for headwater catchments have typically excluded deep groundwater flow based on the assumption that it is a negligible component of the water budget. This study tests this assumption using a coupled surface water–groundwater model to explore the potential contribution of deep groundwater recharge to the bedrock in a snowmelt-dominated headwater catchment (Upper Penticton Creek 241) in the Okanagan Basin, British Columbia. Recharge to the bedrock is estimated at ∼27% of the annual precipitation over the period 2005–2010, recognizing the uncertainty in this estimate due to data limitations, parameter uncertainty and calibration errors. A specified outward flux from the catchment boundary within the saturated zone, representing ∼2% of the annual water budget, was also included in the model. This outward flux contributes to cross-catchment flow and, ultimately, to groundwater inflow to lower elevation catchments in the mountain block. This modeling exercise is one of the first in catchment hydrologic modeling within steep mountainous terrain in which the bedrock is not treated as impermeable, and in which recharge to the bedrock and discharge to the surrounding mountain block were estimated.

Linkages between snow ablation and atmospheric boundary-layer conditions in a semi-arid basin of Western Canada

High-elevation snowpacks provide critical inputs to the hydrological system of mountainous semi-arid regions where summer precipitation is insufficient to maintain adequate discharges for ecological and economic needs. The Okanagan Basin in Western Canada is an example of such a system, as most of the summer streamflow is derived from snowmelt. To better understand how snowmelt events vary as a result of atmospheric conditions, this study developed statistical models using upper-air atmospheric data for evaluating changes in snowpack ablation. Specifically, radiosonde data were statistically linked with detailed ground-based measurements of snowmelt and associated streamflow. Statistical models were developed based on data from the 2007 ablation season and concurrent data from the 850 hPa geopotential height. These models explained 57–68% of the variance in snowmelt for 2007, and were extended to predict snowmelt for the radiosonde period of record (1972–2012). Time-series analyses showed significant trends toward higher winter and spring temperatures, vertical temperature gradients in the atmospheric boundary layer in spring, and earlier dates for snowmelt and freshet initiation. Significant negative trends were also found towards decreasing spring precipitation. More broadly, ablation-season climatic and hydrological variables were significantly positively correlated with the winter and spring Multivariate El Niño Southern Oscillation and Pacific Decadal Oscillation indices, in which the positive (negative) phase was associated with higher (lower) magnitude and frequency of melt events. This combination of strong correlations and significant temporal trends indicates that with projected air-temperature increases, the magnitude and duration of melt events are likely to increase, particularly during favourable phases of the above teleconnections.

Uncertainty-Driven Characterization of Climate Change Effects on Drought Frequency Using Enhanced SPI

The Standardized Precipitation Index (SPI) is a well-established drought index that is based on transforming the interannual distribution of precipitation to a standard normal distribution. Because of its robust statistical basis, SPI is readily applicable to different regions making comparisons between locations and time windows possible. Nevertheless, the usability of SPI results is undermined by shortcomings that are partly resultant from data and model uncertainties. One such shortcoming is the inability of the existing SPI model to include change in variability of interannual precipitation from non-stationary normal – mostly caused by climate change. In addition, epistemic uncertainty in the form of incompleteness in station-wide precipitation records results in heterogeneity and inconsistency in SPI results. The effects of such epistemic uncertainty on the accuracy of estimations of long-term changes in drought frequency are mostly unknown. Given such deficiency, SPI’s procedure and subsequent results remain deterministic and inadequately informative. Here, we introduce modifications to the traditional SPI using Dempster-Shafer theory (DST) to enable modeling and propagation of variability and epistemic uncertainty with the regular SPI procedure. By generalizing the SPI model from a deterministic setting to an “uncertainty-driven setting” provided by DST, this work makes possible: (a) efficiently propagating data uncertainty in interpolation of station-wide precipitation and SPI, and (b) modeling the effects of shift in precipitation normals (due to e.g., climate change) on drought frequency. In addition, the significance of this shift may then be evaluated with respect to the epistemic uncertainty by measuring how much of the surrounding epistemic uncertainty this shift encloses (i.e., “probability of enclosing”). The latter is especially important due to large unknowns already associated with climate change modeling. We implement the model on summer extreme drought for the Okanagan Basin, BC, Canada. For a single general circulation model and scenario (CGCM3 A2) a maximum 7 % increase in summer extreme drought (for 2080s, as per current definition) is estimated with a maximum probability of enclosing of 36 %.

Transient, spatially varied groundwater recharge modeling

The objective of this work is to integrate field data and modeling tools in producing temporally and spatially varying groundwater recharge in a pilot watershed in North Okanagan, Canada. The recharge modeling is undertaken by using the Richards equation based finite element code (HYDRUS‐1D), ArcGIS™, ROSETTA, in situ observations of soil temperature and soil moisture, and a long‐term gridded climate data. The public version of HYDUS‐1D and another version with detailed freezing and thawing module are first used to simulate soil temperature, snow pack, and soil moisture over a one year experimental period. Statistical analysis of the results show both versions of HYDRUS‐1D reproduce observed variables to the same degree. After evaluating model performance using field data and ROSETTA derived soil hydraulic parameters, the HYDRUS‐1D code is coupled with ArcGIS™ to produce spatially and temporally varying recharge maps throughout the Deep Creek watershed. Temporal and spatial analysis of 25 years daily recharge results at various representative points across the study watershed reveal significant temporal and spatial variations; average recharge estimated at 77.8 ± 50.8 mm/year. Previous studies in the Okanagan Basin used Hydrologic Evaluation of Landfill Performance without any attempt of model performance evaluation, notwithstanding its inherent limitations. Thus, climate change impact results from this previous study and similar others, such as Jyrkama and Sykes (2007), need to be interpreted with caution.

Wood dynamics in upland streams under different disturbance regimes

ABSTRACTThis paper presents reach scale large wood (LW) budgets of 12 upland streams in the Okanagan Basin of British Columbia. The study included 100 m long reaches at three wildfire sites and three undisturbed sites in the Interior Douglas‐fir (IDF) biogeoclimatic zone, and three recent Mountain Pine Beetle (MPB) infestation sites and three undisturbed sites in the Montane Spruce (MS) zone. Detailed information on wood recruitment, output and storage were obtained from repeated annual surveys. Recruitment from the riparian zone was found to dominate wood inputs, with fluvial import of secondary importance. In undisturbed streams, wood exhumation was found to be of tertiary importance, but was not observed in disturbed streams. Relative wood length was found to be a strong predictor of wood stability, with wood length to channel width and wood diameter to channel depth ratios of 1:1 forming an approximate maximum threshold of wood mobility. Volumetric decomposition was, on average, a third of the value of fluvial export, and the average residence time of wood in the channels was 20 years. In undisturbed reaches, wood storage indicated a slow depletion of wood from the channels. In the disturbed reaches, wildfire was found to significantly increase annual wood recruitment by more than an order of magnitude over undisturbed or control streams. MPB had not significantly increased LW recruitment, but is expected to increase over the coming decades. Storage rates at the disturbed streams indicated a net accumulation of wood over the study period. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Estimating regional-scale fractured bedrock hydraulic conductivity using discrete fracture network (DFN) modeling

Estimating bedrock hydraulic conductivity of regional fractured aquifers is challenging due to a lack of aquifer testing data and the presence of small and large-scale heterogeneity. This study provides a novel approach for estimating the bedrock hydraulic conductivity of a regional-scale fractured bedrock aquifer using discrete fracture network (DFN) modeling. The methodology is tested in the mountainous Okanagan Basin, British Columbia, Canada. Discrete fractures were mapped in outcrops, and larger-scale fracture zones (corresponding to lineaments) were mapped from orthophotos and LANDSAT imagery. Outcrop fracture data were used to generate DFN models for estimating hydraulic conductivity for the fractured matrix (Km). The mountain block hydraulic conductivity (Kmb) was estimated using larger-scale DFN models. Lineament properties were estimated by best fit parameters for a simulated pumping test influenced by a fracture zone. Unknown dip angles and directions for lineaments were estimated from the small-scale fracture sets. Simulated Km and Kmb values range from 10–8 to 10–7 m/s and are greatest in a N–S direction, coinciding with the main strike direction of Okanagan Valley Fault Zone. Kmb values also decrease away from the fault, consistent with the decrease in lineament density. Simulated hydraulic conductivity values compare well with those estimated from pumping tests.

Intermittent and Perennial Streamflow Regime Characteristics in the Okanagan

Streamflow data from ten Water Survey of Canada gauging stations were analyzed to characterize streamflow regimes in the Okanagan Basin (British Columbia). The differences in the streamflow regime characteristics of the perennial and intermittent streams were subtle, except for the obvious difference in summer low flows. The intermittent streams tended to have faster recessions after spring freshet, steeper flow duration curves, a slightly earlier median day of the year of the start of the freshet, and more variable discharge in fall. In years with high fall precipitation, discharge was also high during fall for the intermittent streams but in other years it was very low. Discharge on August 15th was lower or similar to streamflow on March 15th for the intermittent stream, whereas it was much higher on August 15th for the perennial streams. These subtle streamflow regime differences point to differences in flow pathways, groundwater contributions to streamflow, and residence times between the intermittent and perennial watersheds, and may have important ecological implications.

Future Water Supply and Demand in the Okanagan Basin, British Columbia: A Scenario-Based Analysis of Multiple, Interacting Stressors

Surface water is critical for meeting water needs in British Columbia’s Okanagan Basin, but the timing and magnitude of its availability is being altered through climate and land use changes and growing water demand. Greater attention needs to be given to the multiple, interacting factors occurring and projected to occur in this region if water is going to be sustainably provisioned to human users and available for ecosystem needs. This study contributes to that goal by integrating information on physical, biological and social processes in order to project a range of possible changes to surface water availability resulting from land-use, climatic and demographic change, as well as from Mountain Pine Beetle infestation. An integrated water management model (Water Evaluation and Planning system, WEAP) was used to consider future scenarios for water supply and demand in both unregulated and reservoir-supported streams that supply the District of Peachland. Results demonstrate that anticipated future climate conditions will critically reduce streamflow relative to projected uses (societal demand and ecological flow requirements). The surficial storage systems currently in place were found unable to meet municipal and instream flow needs during “normal” precipitation years by the 2050s. Improvements may be found through demand reduction, especially in the near term. Beyond the implications for the District of Peachland, this work demonstrates a method of using an accessible modeling tool for integrating knowledge from the fields of climate science, forest hydrology, water systems management and stream ecology to aid in water and land management decision-making.

Historical Trends in Annual Water Yields for the Okanagan Basin, British Columbia, Canada

The Okanagan Basin in south-central British Columbia, Canada, includes the Okanagan River watershed upstream from the outlet of Osoyoos Lake, with a total area of 8,046 km^2^. Over the past century, the population of the Basin has grown rapidly, and this trend is expected to continue. Water management issues attract significant attention in the region, given projected declines in supply and increases in demand. Historical streamflow data was obtained for three hydrometric stations on the Okanagan River between the outlet of Okanagan Lake at Penticton and near the U.S. border at Oliver. Collectively, the historical data series indicate no temporal changes in regional annual water yields for the Okanagan Basin over the past century, despite large increases in population and agricultural activity over this time. Although rapid and extensive human settlement and development of the region, along with possible climate change signatures during the 20th century, has potentially altered the inflow hydrographs to tributary streams in the Basin, the overall water yield of the region appears to be stable and possibly increasing.

Historical Trends in Annual Water Yields for the Okanagan Basin, British Columbia, Canada

AbstractThe Okanagan Basin in south-central British Columbia, Canada, includes the Okanagan River watershed upstream from the outlet of Osoyoos Lake, with a total area of 8,046 km^2^. Over the past century, the population of the Basin has grown rapidly, and this trend is expected to continue. Water management issues attract significant attention in the region, given projected declines in supply and increases in demand. Historical streamflow data was obtained for three hydrometric stations on the Okanagan River between the outlet of Okanagan Lake at Penticton and near the U.S. border at Oliver. Collectively, the historical data series indicate no temporal changes in regional annual water yields for the Okanagan Basin over the past century, despite large increases in population and agricultural activity over this time. Although rapid and extensive human settlement and development of the region, along with possible climate change signatures during the 20th century, has potentially altered the inflow hydrographs to tributary streams in the Basin, the overall water yield of the region appears to be stable and possibly increasing.