English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The U.S. Geological Survey’s Soil-Water-Balance (SWB) code was developed as a tool to estimate distribution and timing of net infiltration out of the root zone by means of an approach that uses readily available data and minimizes user effort required to begin a SWB application. SWB calculates other components of the water balance, including soil moisture, reference and actual evapotranspiration, snowfall, snowmelt, canopy interception, and crop-water demand. SWB is based on a modified Thornthwaite-Mather soil-waterbalance approach, with components of the soil-water balance calculated at a daily time step. Net-infiltration calculations are computed by means of a rectangular grid of computational elements, which allows the calculated infiltration rates to be imported into grid-based regional groundwater-flow models. SWB makes use of gridded datasets, including datasets describing hydrologic soil groups, moisture-retaining capacity, flow direction, and land use. Climate data may be supplied in gridded or tabular form. The SWB 2.0 code described in this report extends capabilities of the original SWB version 1.0 model by adding new options for representing physical processes and additional data input and output capabilities. New methods included in SWB 2.0 allow for direct gridded input of externally calculated water-budget components (fog, septic, and storm-sewer leakage), simulation of canopy interception by several alternative processes, and a crop-water demand method for estimating irrigation amounts. New input and output capabilities allow for grids with differing spatial extents and projections to be combined without requiring the user to resample and resize the grids before use. Introduction Accurate estimates of the spatial and temporal distribution of groundwater recharge are important for many types of hydrologic assessments, including assessments that concern water availability, water-quality protection, streamflow and riparian-ecosystem management, aquifer replenishment, groundwater-flow modeling, and contaminant transport; these recharge estimates often are key to understanding effects of land-use change in urban, industrial, and agricultural regions. With increasing demand for science-supported hydrologic management comes an increased need for robust and practical methods to quantify groundwater recharge rates (Scanlon and others, 2002). To fill this need, Dripps and Bradbury (2007) created a spreadsheet code that calculates components of the soil-zone water balance at a daily time step by means of a modified version of the Thornthwaite-Mather soil-moisture-balance approach (Thornthwaite, 1948; Thornthwaite and Mather, 1957). The primary output of the water-balance code is net infiltration out of the root zone. In areas where groundwater is close to the surface (less than 10 meters), net infiltration may be assumed to become recharge. In areas with deeper groundwater tables, or for dynamic models that require simulation of recharge timing, MODFLOW’s Unsaturated Zone Flow Package (Niswonger and others, 2006) may be used to simulate the transport of net infiltration to the groundwater table. 1Utilities Department, City of Bloomington, Indiana. 2 SWB Version 2.0—A Soil-Water-Balance Code for Estimating Net Infiltration and Other Water-Budget Components Data requirements for the original water-balance code included the following several commonly available tabular and gridded data types: (1) precipitation and temperature, (2) land-use classification, (3) hydrologic soil group, (4) flow direction, and (5) soil-water capacity. The data and required formats were designed to take advantage of widely available geographic information systems (GIS) datasets and file structures. To increase ease of use, reduce reliance on proprietary software, and increase the size of model domain that could be simulated, the U.S. Geological Survey (USGS) translated the original soil-water-balance code from the spreadsheet Visual Basic to modern Fortran 2008; the Fortran version was called the Soil-Water-Balance (SWB) code version 1.0 (Westenbroek and others, 2010). SWB 1.0 was used to estimate net infiltration out of the root zone in a wide variety of environmental settings; for examples, see Feinstein and others (2010) or Hunt and others (2016). The SWB code has evolved since the original release, with the addition of crop-water demand calculations and some of the functionality of the Hawaii water-budget code (Izuka and others, 2010). This report documents version 2.0 of the SWB software, hereafter referred to as SWB. Background and Terminology Standard terminology is not available for use in discussions of the water-budget components that result in groundwater recharge. The nomenclature and following definitions from Healy (2010) are used in this report. Potential recharge.—Water that has infiltrated into the root zone. Potential recharge may leave the bottom of the root zone, eventually becoming recharge. Alternatively, potential recharge may be removed from the soil column by means of evaporation and transpiration. Net infiltration.—Water that has escaped the evapotranspiration sinks of the root zone, some portion of which will eventually find its way to the groundwater table. Groundwater recharge.—Water that actually crosses the water table. This report uses slightly different terminology than Westenbroek and others (2010). In both reports, however, the terms used underscore the fact that SWB does not simulate unsaturated-zone processes beneath the root zone. When the unsaturated zone is sufficiently thick, it can impart appreciable lags between the time when water leaves the bottom of the root zone and the time when water crosses the water table and enters the groundwater system (Healy, 2010; Hunt and others, 2008; Nimmo and others, 2005); under some conditions, separate net-infiltration events coalesce in the unsaturated zone and enter the water table as a single recharge event. Therefore, the output of the SWB code is here referred to as “net infiltration” rather than “groundwater recharge”, in keeping with Healy’s (2010) usage. The distinction between infiltration and recharge has been explored in detail by others; see for example Anderson and others (2015, p. 232–234). Net infiltration and related groundwater recharge can vary with time and space. Site-specific measurements of net infiltration and recharge, if available, are difficult to upscale for application in regional-scale problems. Yet, in groundwater-modeling problems, application of physically based, spatially variable recharge values to the water table have been determined to improve model performance (Jyrkama and Sykes, 2007; Hunt and others 2008). A soil-water-balance modeling approach is currently the preferred method for distributing net infiltration in space and time for use in applied groundwater modeling (Anderson and others, 2015, p. 232). The temporal discretization used in the soil-water-balance model should not be overly coarse. For example, Rushton and Ward (1979) determined that running a soil-water-balance calculation with monthly time steps gave net-infiltration values 25 percent less than soil-water-balance calculations using daily values. Many soil-water-balance models are described in the literature, most developed for specific applications. Soilwater-balance models have been developed to evaluate crop irrigation requirements and impacts (Boisvert, 1990; Braud and others, 2013; Jensen, 1969; Kendy and others, 2003), crop yield prediction (Akinremi and others, 1996), and landfill cover design (Schroeder and others, 1994), and to estimate net infiltration (Batelaan and De Smedt, 2001; Eilers and others, 2007; Finch, 2001; Fitzsimons and Misstear, 2006; Jyrkama and others, 2002; Lee and others, 2006; Manghi and others, 2009). Within the USGS, many different water-balance models have been used as a means to estimate net infiltration. The Yucca Mountain Project of the 1980s and 1990s produced the INFIL 3.0 model (U.S. Geological Survey, 2008). The Basin Characterization Model has been applied to significant tracts of the western United States (Flint and others, 2014; Flint and Flint, 2007). A similar model was developed and applied in Montana, Idaho, and Washington State (not shown) (Bauer and Vaccaro, 1987; Bauer and Vaccaro, 1990). A custom water balance model has been applied to the Hawaiian Islands (not shown) for decades (Izuka and others, 2010). Another custom water balance model was applied to the central Midwest regional aquifer system, with special emphasis on estimating consumptive use of water and the resulting impact on recharge (Dugan and Peckenpaugh, 1985). These models have generally been developed with specific environmental settings in mind (Yucca Mountain, Hawaiian Islands) but include processes and algorithms that may be suited for future versions of the SWB code documented in this report.

SWB Version 2.0—A soil-water-balance code for estimating net infiltration and other water-budget components