Hydrological Processes

doi: 10.1002/hyp.10654pmid: N/A

Zeiger, Sean; Hubbart, Jason A.; Anderson, Stephen H.; Stambaugh, Michael C.

doi: 10.1002/hyp.10617pmid: N/A

Hydrologic models that rely on site specific linear and non‐linear regression water temperature (Tw) subroutines forced solely with observed air temperature (Ta) may not accurately estimate Tw in mixed‐use urbanizing watersheds where hydrogeological and land use complexity may confound common Tw regime assumptions. A nested‐scale experimental watershed study design was used to test Tw model predictions in a representative mixed‐use urbanizing watershed of the central USA. The linear regression Tw model used in the Soil and Water Assessment Tool (SWAT), a non‐linear regression Tw model, and a process‐based Tw model that accounts for watershed hydrology were evaluated. The non‐linear regression Tw model tested at a daily time step performed significantly (P < 0.01) better than the linear Tw model currently used in SWAT. Both regression Tw models overestimated Tw in lower temperature ranges (Tw < 10.0 °C) with percent bias (PBIAS) values ranging from −28.2% (non‐linear Tw model) to −66.1% (linear regression Tw model) and underestimated Tw in the higher temperature range (Tw > 25.0 °C) by 3.2%, and 7.2%, respectively. Conversely, the process‐based Tw model closely estimated Tw in lower temperature ranges (PBIAS = 4.5%) and only slightly underestimated Tw in the higher temperature range (PBIAS = 1.7%). Findings illustrate the benefit of integrating process‐based Tw models with hydrologic models to improve model transferability and Tw predictive confidence in urban mixed‐land use watersheds. The findings in this work are distinct geographically and in terms of mixed‐land use complexity and are therefore of immediate value to land‐use managers in similarly urbanizing watersheds globally. Copyright © 2015 John Wiley & Sons, Ltd.

Cao, Guoliang; Zheng, Chunmiao

doi: 10.1002/hyp.10631pmid: N/A

Growing demand on groundwater resources and the semi‐arid climate in the North China Plain (NCP) highlight the need for improved understanding of connections between regional climate change and groundwater recharge. Hydrologic time series of precipitation and groundwater levels were analyzed in three representative geographical zones throughout the NCP for the period of 1960–2008 using trend analysis and spectral analysis methods. A significant change point around 1975 is followed by a long‐term decline trend in precipitation time series, which coincides with the Pacific Decadal Oscillation positive phase. However, the magnitudes of groundwater level variability due to heavy pumping overwhelm the low‐frequency signal of groundwater levels. Nonlinear trends that related to long‐term climatic variability and anthropogenic activities are removed by using the Singular Spectrum Analysis method. Spectral analyses of the detrended residuals demonstrate significant short‐term oscillations at the frequencies of 2–7 years, which have strong correlations with the El Niño–Southern Oscillation modes. This study contributes to improved understanding of dynamic relationship between groundwater and climate variability modes in the NCP and demonstrates the importance of reliable detrending methods for groundwater levels that are affected greatly by pumping. Copyright © 2015 John Wiley & Sons, Ltd.

Ferencz, Beata; Dawidek, Jarosław

doi: 10.1002/hyp.10618pmid: N/A

The general role of river water input in shaping the basic morphometric parameters of floodplain lakes has been previously investigated. However, the process has not been quantitatively described in detail. This study is the first attempt in the literature to determine the allometric relation between fluvial impulse, expressed as Fluvial Connectivity Quotient, and morphometric parameters of six floodplain lakes of Bug River valley in the period 1952–2014. This relationship is given by Y = aXb, from which the value of b exponent was analysed to determine the strength of the allometric relation. Extreme values of allometric compounds during the time period under study ranged from 5.99 to −4.91. Volume was the morphometric parameter showing the highest variability in all the lakes. General similarity in allometric relations was observed in the lakes under study. During analysis, no long‐term trends were observed in the relationship between the Fluvial Connectivity Quotient and morphometric parameters. The results obtained show that fluvial impulse was the factor determining the variability of morphometric parameters of the lakes. Direct catchments topography of lake has periodically (during limnophase periods) played a significant role in shaping the morphometry of floodplain lakes. The most stable allometric relations occurred in a confluent lake, with a low limnological effective rise value and consequently, relatively long potamophase periods.Copyright © 2015 John Wiley & Sons, Ltd.

Guan, Mingfu; Sillanpää, Nora; Koivusalo, Harri

doi: 10.1002/hyp.10624pmid: N/A

This study explored the hydrological impacts of urbanization, rainfall pattern and magnitude in a developing catchment. The Stormwater Management Model was parameterized, calibrated and validated in three development phases, which had the same catchment area (12.3 ha) but different land use intensities. The model calibration and validation by using sub‐hourly hydro‐meteorological data demonstrated a good performance of the model in predicting stormwater runoff in the different development phases. Based on the results, a threshold between minor and major rainfall events was identified and conservatively determined to be about 17.5 mm in depth. Direct runoff for minor storm events has a linear relationship with rainfall; however, events with a rainfall depth greater than the threshold yield a rainfall–runoff regression line with a clearly steeper slope. The difference in urban runoff generation between minor and major rainfall events diminishes with the increase of imperviousness. Urbanization leads to an increase in the production of stormwater runoff, but during infrequent major storms, the runoff contribution from pervious surfaces reduces the runoff changes owing to urbanization. Rainfall pattern exerts an important effect on urban runoff, which is reflected in pervious runoff. With the same magnitude, prolonged rainfall events with unvarying low intensity yield the smallest peak flow and the smallest total runoff, yet rainfall events with high peak intensity produce the largest runoff volume. These results demonstrate the different roles of impervious and pervious surfaces in runoff generation, and how runoff responds to rainstorms in urban catchments depends on hyetograph and event magnitude. Furthermore, the study provides a scientific basis of the design guideline sustainable urban drainage systems, which are still arbitrary in many countries. Copyright © 2015 John Wiley & Sons, Ltd.

Fujimoto, Masamitsu; Ohte, Nobuhito; Kawasaki, Masatoshi; Osaka, Ken'ichi; Itoh, Masayuki; Ohtsuka, Izumi; Itoh, Masami

doi: 10.1002/hyp.10558pmid: N/A

Groundwater movements in volcanic mountains and their effects on streamflow discharge and representative elementary area (REA) have remained largely unclear. We surveyed the discharge and chemical composition of spring and stream water in two catchments: the Hontani river (NR) catchment (6.6 km2) and the Hosotani river (SR) catchment (4.0 km2) at the southern part of Daisen volcano, Japan. Daisen volcano is a young volcano (17 × 103 years) at an early stage of erosion. Our study indicated that deep groundwater that moved through thick lava and pyroclastic flows and that could not be explained by shallow movements controlled by surface topography contributed dominantly to streamflow at larger catchment areas. At the NR catchment, the deep groundwater contribution clearly increased at a catchment boundary defined by an area of 3.0 km2 and an elevation of 800 m. At the SR catchment, the contribution deep groundwater to the stream also increased suddenly at a boundary threshold of 2.0 and 700 m. Beyond these thresholds, the contributions of deep bedrock groundwater remained constant, indicating that the REA is between 2 and 3 km2 at the observed area. These results indicate that the hydrological conditions of base flow were controlled mainly by the deep bedrock groundwater that moved through thick lava and pyroclastic flows in the undissected volcanic body of the upper part of the catchment. Our study demonstrates that deep and long groundwater movements via a deep bedrock layer including thick deposits of volcanic materials at the two catchments on Daisen volcano strongly determined streamflow discharge instead of the mixing of small‐scale hydrological conditions. Copyright © 2015 John Wiley & Sons, Ltd.

Jimenez‐Martinez, Joaquin; Smith, Martin; Pope, David

doi: 10.1002/hyp.10619pmid: N/A

Current climate change models for the southeast UK predict changing rainfall patterns, with increased incidence of extreme events. The chalk aquifer in the UK and northern France is susceptible to groundwater‐induced flooding under such conditions. In this methodological study we apply a frequency domain analysis approach to the chalk aquifer to derive a transfer function between effective rainfall and groundwater level from 7 years of monitoring data from the North Heath Barn site, near Brighton. The derived transfer function was calibrated and validated against monitoring data and then used to predict groundwater level for rainfall models for high, medium and low emission scenarios from the UKCP09 database. The derived transfer function is most closely comparable to the linear aquifer model, despite evidence for both matrix and fracture or karst water flow in the chalk, with transmissivity and unconfined storativity at the catchment scale of 1548 m2 day−1 and 1.6 × 10−2. The application of the transfer function to UKCP09 rainfall data suggests that groundwater‐induced flooding may be about four times more frequent by 2040–2069 compared with 1961–1990 and seven times more frequent by 2070–2099. The model data also suggest an increase in the duration of groundwater minima relative to the reference period. Compared to deterministic modelling which requires detailed knowledge of aquifer heterogeneity and processes, the transfer function approach, although with limitations, is simpler, incorporating these factors into the analysis through frequency and phase coefficients, and thus may have the potential for groundwater risk assessment in other areas. Copyright © 2015 John Wiley & Sons, Ltd.

Welch, Christopher M.; Stoy, Paul C.; Rains, F. Aaron; Johnson, Aiden V.; McGlynn, Brian L.

doi: 10.1002/hyp.10638pmid: N/A

Mountain snowpacks provide most of the annual discharge of western US rivers, but the future of water resources in the western USA is tenuous, as climatic changes have resulted in earlier spring melts that have exacerbated summer droughts. Compounding changes to the physical environment are biotic disturbances including that of the mountain pine beetle (MPB), which has decimated millions of acres of western North American forests. At the watershed scale, MPB disturbance increases the peak hydrograph, and at the stand scale, the ‘grey’ phase of MPB canopy disturbance decreases canopy snow interception, increases snow albedo, increases net shortwave radiation, and decreases net longwave radiation versus the ‘red’ phase. Fewer studies have been conducted on the red phase of MPB disturbance and in the mixed coniferous stands that may follow MPB‐damaged forests. We measured the energy balance of four snowpacks representing different stages of MPB damage, management, and recovery: a lodgepole pine stand, an MPB‐infested stand in the red phase, a mixed coniferous stand (representing one successional trajectory), and a clear‐cut (representing reactive management) in the Tenderfoot Creek Experimental Forest in Montana, USA. Net longwave radiation was lower in the MPB‐infested stand despite higher basal area and plant area index of the other forests, suggesting that the desiccated needles serve as a less effective thermal buffer against longwave radiative losses. Eddy covariance observations of sensible and latent heat flux indicate that they are of similar but opposite magnitude, on the order of 20 MJ m−2 during the melt period. Further analyses reveal that net turbulent energy fluxes were near zero because of the temperature and atmospheric vapour pressure encountered during the melt period. Future research should place snow science in the context of forest succession and management and address important uncertainties regarding the timing and magnitude of needlefall events. Copyright © 2015 John Wiley & Sons, Ltd.

Rajib, Mohammad Adnan; Merwade, Venkatesh

doi: 10.1002/hyp.10639pmid: N/A

The objective of this study is to incorporate a time‐dependent Soil Moisture Accounting (SMA) based Curve Number method (SMA_CN) in Soil and Water Assessment Tool (SWAT) and compare its performance with the existing CN method in SWAT by simulating the hydrology of two agricultural watersheds in Indiana, USA. Results show that fusion of the SMA_CN method causes decrease in runoff volume and increase in profile soil moisture content, associated with larger groundwater contribution to the streamflow. In addition, the higher amount of moisture in the soil profile slightly elevates the actual evapotranspiration. The SMA‐based SWAT configuration consistently produces improved goodness‐of‐fit scores and less uncertain outputs with respect to streamflow during both calibration and validation. The SMA_CN method exhibits a better match with the observed data for all flow regimes, thereby addressing issues related to peak and low flow predictions by SWAT in many past studies. Comparison of the calibrated model outputs with field‐scale soil moisture observations reveals that the SMA overhauling enables SWAT to represent soil moisture condition more accurately, with better response to the incident rainfall dynamics. While the results from the modification of the CN method in SWAT are promising, more studies including watersheds with various physical and climatic settings are needed to validate the proposed approach. Copyright © 2015 John Wiley & Sons, Ltd.

Kellner, Elliott; Hubbart, Jason

doi: 10.1002/hyp.10645pmid: N/A

Given the importance of groundwater temperature to the biogeochemical health of aquatic ecosystems, a floodplain study was implemented to improve understanding of rural land use impacts on shallow groundwater (SGW) temperature. Study sites included a historic agricultural field (Ag) and bottomland hardwood forest (BHF), each with nine piezometers in an 80 × 80 m grid. Piezometers were equipped with pressure transducers to monitor SGW temperature and level at 30 min intervals during the 2011, 2012, 2013, and 2014 water years. The study is one of the first to utilize long‐term, continuous, automated, in situ monitoring to investigate rural land use impacts on shallow groundwater temperatures. Average SGW temperature during the study period was 11.1 and 11.2 °C at the Ag and BHF sites, respectively. However, temperature range at the Ag site was 72% greater than at the BHF site. Results indicate a greater responsiveness to seasonal climate fluctuations in Ag site SGW temperature related to absence of forest canopy. Patterns of intra‐site groundwater temperature differences at both study sites illustrate the influence of stream–aquifer thermal conduction and occasional baseflow reversals. Considering similar surface soil temperature amplitudes and low average groundwater flow values at both sites, results suggest that contrasting rates of plant water use, groundwater recharge, and subsurface hydraulic conductivity are likely mechanistic causes for the observed SGW temperature differences. Results highlight the long‐term impact of forest removal on subsurface hydrology and groundwater temperature regime. Copyright © 2015 John Wiley & Sons, Ltd.