M. Levent Kavvas

University of California, Davis | UCD · Department of Civil and Environmental Engineering

Groundwater storage in aquifers has become a vital water source due to water scarcity in recent years. However, aquifer systems are full of uncertainties, which inevitably propagate throughout the modeling computations, mainly reducing the reliability of the model output. This study develops a novel two-dimensional stochastic confined groundwater f...

Subsurface flow is a critical component in the hydrological cycle, since it controls the quantity and timing of surface runoff and groundwater flow. Field studies have shown the fundamental influence of the bedrock surface geometry on subsurface stormflow (SSSF) and that the SSSF process consists of at least two major components: the matrix flow co...

This study develops the governing equations of unsteady multi-dimensional incompressible and compressible flow in fractional time and multi-fractional space. When their fractional powers in time and in multi-fractional space are specified to unit integer values, the developed fractional equations of continuity and momentum for incompressible and co...

Throughout the world, louver‐bypass systems are a common method for fish protection at water diversion sites. Their performance has been evaluated for pelagic, strong‐swimming teleost fishes, but limited information exists regarding the effectiveness of louvers for guiding sturgeon, despite being a globally threatened taxon. This study used control...

Estimation of probable maximum flood (PMF) is a crucial process in water resources management and in the design of large hydraulic structures. However, there are uncertainties in the estimation of hydrologic conditions that contribute to extreme floods. In particular, this is the case in snow-dominated regions, as surface air temperature and wind s...

Estimated extreme precipitation and floods provide crucial information for both the design of large hydraulic structures and water resources management. This study aims to estimate, in a series of numerical experiments, the probable maximum precipitation associated with extreme rain events over seven watersheds in the central/southern Sierra Nevada...

This study examined the hydrological/meteorological controls on large wildfires > 10,000 acres (40.5 km2) during 2017–2020 in Northern California at spatial and temporal scales of the target wildfires’ occurrence or growth. This study used the following simple indices for analysis: Moisture Deficit Index (MDI) computed by dividing vapor pressure de...

It is important to assess the reliability of the high resolution climate variables that are 22 downscaled from a coarse grid dataset such as GCMs' outputs or reanalysis data, and are used as 23 input for hydrologic applications, by means of comprehensive evaluations based on various types 24 of observations from different data sources. In this stud...

Outmigrating, juvenile Chinook salmon Oncorhynchus tshawytscha, with access to floodplains (e.g., Yolo Bypass California, USA), grow faster than those restricted to the main channel of the Sacramento River. How these young salmon might use rooted, vegetative structure (e.g., to decrease energy expenditures) while holding positions in flowing water...

Data scarcity is one of the major constraints for hydrological modeling at a mountainous region with complex terrains. In this study, WRF (Weather Research and Forecasting model) model was configured to produce high-resolution atmospheric data for spatial modeling of snow at seven watersheds in central/southern Sierra Nevada. The configured WRF mod...

The Probable Maximum Precipitation (PMP) estimation for long durations during winter and spring seasons is important to develop the Probable Maximum Flood for snowmelt-driven regions since extreme floods are often characterized by snow-accumulation and snowmelt processes rather than by a single rainstorm event. Although several studies have estimat...

Can be freely downloaded from https://www.mdpi.com/2073-4441/13/4/511 Significant deviations from standard Boltzmann scaling, which corresponds to normal or Fickian diffusion, have been observed in the literature for water movement in porous media. However, as demonstrated by various researchers, the widely used conventional Richards equation can...

Water storage requirements in the Mediterranean region vary in time and are strongly affected by the local geography and climate conditions. The objective of this study is to assess the implications of climate change on the water balance of an agricultural reservoir in a Mediterranean-climate basin in Turkey throughout the 21st century. A monthly d...

Long-term, high spatial and temporal resolution atmospheric and hydrologic data are crucial for water resource management. However, reliable high-quality precipitation and hydrologic data are not available in various regions around the world. This is, in particular, the case in transboundary regions, which have no formal data sharing agreement amon...

Extreme flood events are disastrous and can cause serious damages to society. Flood frequency obtained based on historical flow records may also be changing under future climate conditions. The associated flood inundation and environmental transport processes will also be affected. In this study, an integrated numerical modeling framework is propos...

This paper presents a case study on the impact of dynamic management of wetland storage on downstream flood control at the Cypress Creek Watershed in Houston, Texas. Dynamic storage management is performed by optimizing the schedule of flow releases from managed wetlands for minimizing downstream inundation. The novelty of this study is to increase...

This paper presents a case study on the impact of the size and location of wetlands on watershed-scale flood control utilizing the Cypress Creek Watershed in Houston, Texas as the study area. Wetlands of different sizes were implemented at different locations (upstream, midstream, and downstream) of the watershed and corresponding hydrologic and hy...

In this study, a dimensionally consistent governing equation of transient unconfined groundwater flow in fractional time and multi-fractional space is developed. First, a fractional continuity equation for transient unconfined groundwater flow is developed in fractional time and space. For the equation of groundwater motion within a multi-fractiona...

In this article, a method to find evolution equations for the probability density function (pdf) of a stochastic process governed by a nonlinear stochastic ordinary differential equation is presented. According to Van Kampen’s lemma, the pdf of a stochastic process is equal to the ensemble average of the phase-space density. The conservation of the...

Prediction of sediment discharge transported within flow is strongly needed in order to provide measures for a well-established erosion control and water quality management practice. Initiated by runoff generation and erosion processes sediment transport is influenced by microtopography over hillslopes of hydrological watersheds. Consideration of m...

The study of solute transport in rivers is of environmental significance, since solute transported in river flows may affect the river water quality conditions. Solute transport in natural flows is a challenging process to be investigated, given natural flows usually indicate uncertainty in space and time. Two-dimensional models are more preferable...

The concept of Probable Maximum Precipitation (PMP) is widely used for the design and risk assessment of water resource infrastructure. Despite its importance, past attempts to estimate PMP have fully investigated the realism of design maximum storms from a meteorological perspective. This study investigates estimating PMP with realistically maximi...

The entrainment and impingement of fish into water diversion infrastructure is one of the several factors contributing to their decline. Here, controlled experiments assessed the potential for a behavioral guidance device [a light-emitting diode (LED) light array] strobing at various spectra to reduce the entrainment of juvenile Chinook salmon (Onc...

In this study, a regional climate model was used to dynamically downscale 15 future climate projections from three GCMs covering four emission scenarios (SRES B1, A1FI, A1B, A2) based on Coupled Model Intercomparison Project phase 3 (CMIP3) datasets to 6-km horizontal resolution over the whole Peninsular Malaysia. Impacts of climate change in the 2...

In this study, a dimensionally-consistent governing equation of transient unconfined groundwater flow in fractional time and multi-fractional space is developed. First, a fractional continuity equation for transient unconfined groundwater flow is developed in fractional time and space. For the equation of groundwater motion within a multi-fractiona...

In this article, numerical experiments are performed to investigate the effects of increasing atmospheric moisture on the precipitation depth (PD) produced by Hurricane Ivan (2004) over a target area, chosen as the drainage basin of the city of Asheville, NC. Atmospheric moisture was increased indirectly by increasing the sea surface temperature (S...

Solute transport by river and stream flows in natural environment has significant implication on water quality and the transport process is full of uncertainties. In this study, a stochastic one-dimensional solute transport model under uncertain open-channel flow conditions is developed. The proposed solute transport model is developed by upscaling...

A new methodology is implemented to obtain the probability density function of the water table height in the subsurface stormflow process, while considering the hydraulic conductivity as a random function. The methodology incorporates the Boussinesq equation that describes the subsurface stormflow process into a Fokker-Plank equation, which estimat...

Can be downloaded from link below (50 days' free access): "https://authors.elsevier.com/c/1ZAI2_17GgHSA8 ". A point-location-based analysis of future climate change impacts on snow accumulation and melting processes was conducted over three study watersheds in Northern California during a 90-year future period by means of snow regime projections....

In this article, a dynamical downscaling (DD) procedure is proposed to downscale tropical cyclones (TCs) from a general circulation model, with the goal of investigating inland intense precipitation from these storms in the future. This DD procedure is sequential as it is performed from the large scale to the small scale within a one-way nesting mo...

Tropical cyclones (TCs) are intense atmospheric vortices that form over the warm tropical oceans. They are recognized for their ability to generate intense precipitation that may in turn create disastrous floods. This article first assesses the suitability of a regional atmospheric model, the Weather Research and Forecasting (WRF) model, to simulat...

In this article, a method for the storm transposition of tropical cyclones is presented. This method is physically based as it uses a regional atmospheric model to reconstruct the precipitation depth field from a tropical cyclone, thus crucially conserving the mass, momentum and energy in the system. In this physically based storm transposition met...

The impacts of climate change on snow distribution through the 21st century were investigated over three mountainous watersheds in Northern California by means of a physically-based snow distribution model. The future climate conditions during a 90-year future period from water year 2010 to 2100 were obtained from 13 future climate projection reali...

Long-term, high spatial and temporal resolution of atmospheric data is crucial for with the purpose of reducing the effects of hydro-meteorological risks on human society in an economically and environmentally sustainable manner. However, such information usually is limited in transboundary regions due to different governmental policies, and to con...

Impact of future climate change on watershed-scale precipitation was investigated over Northern California based on future climate projections by means of the dynamical downscaling approach. Thirteen different future climate projection realizations from two general circulation models (GCMs: ECHAM5 and CCSM3) based on four emission scenarios (SRES A...

Estimation of the extreme precipitation over a target watershed under a changing climate would be necessary to design safe large hydraulic structures. For this purpose, the Maximum Precipitation (MP) estimation approach was applied to the American River watershed (ARW) in Northern California under several future climate conditions over 90 water yea...

The Gediz Basin is a Mediterranean watershed along the Aegean coast of Turkey, in which the most important economic activity is agriculture. Over the last few decades, this basin has been experiencing water-related problems such as water scarcity and competing use of water. This study assesses the impact of future climate change on the availability...

Located along the western coast of Turkey, the Gediz Basin counts on agriculture as its most important economic activity. Over the last few decades, the basin has been facing water-related problems, such as water scarcity and competing use of water. However, an investigation of possible future water demands and droughts is expected to be helpful fo...

Mesoscale convective systems (MCSs) are large clusters of thunderstorms that act as a single system generating localized extreme precipitation and causing disastrous flooding and destruction in the central United States. To enhance our modeling of such storm events, especially under future climate projections, this study focuses on modeling MCSs th...

The Fokker-Planck equation (FPE) methodology was applied to the transient state confined groundwater flow equation under the initial and boundary conditions leading to the Theis problem. The differential Theis equation was transformed to the FPE form, which describes the evolution of the probability density function of the state variable for this s...

The Saint-Venant equations are commonly used as the governing equations to solve for modeling the spatially varied unsteady flow in open channels. The presence of uncertainties in the channel or flow parameters renders these equations stochastic, thus requiring their solution in a stochastic framework in order to quantify the ensemble behavior and...

The characteristic form of the Saint-Venant equations is solved in a stochastic setting by using a newly proposed Fokker–Planck Equation (FPE) methodology. This methodology computes the ensemble behavior and variability of the unsteady flow in open channels by directly solving for the flow variables' time–space evolutionary probability distribution...

In order to model non‐Fickian transport behavior in groundwater aquifers, various forms of the time‐space fractional advection‐dispersion equation have been developed and used by several researchers in the last decade. The solute transport in groundwater aquifers in fractional time‐space takes place by means of an underlying groundwater flow field....

Soil properties play an important role in watershed hydrology and environmental modeling. In order to model realistic hydrologic processes, it is necessary to obtain compatible soil data. This study introduces a new method that integrates global soil databases with land use/land cover (LULC) databases to better represent saturated hydraulic conduct...

Certain methods of Probable Maximum Precipitation (PMP) estimation such as the generalized estimation method involve the transposition to the target area of intense storms that occurred in adjacent areas. This storm transposition step is based on the assumption that it is possible to delineate a meteorologically homogeneous region (World Meteorolog...

California's interconnected water system is one of the most advanced water management systems in the world, and understanding of long-term trends in atmospheric and hydrologic behavior has increasingly being seen as vital to its future well-being. Knowledge of such trends is hampered by the lack of long-period observation data and the uncertainty s...

One of the major challenges in water resources research is to understand the impact of climate change on hydrology. In Thailand, upper Ping river basin is one of the major resources supply water to a major rice bowl, Chao Phraya basin area. In this study, the effects of climate change on hydrology was utilized by using SRES-climate scenarios during...

In this study dimensionally-consistent governing equations of continuity and motion for transient soil 11 water flow and soil water flux in fractional time and in fractional multiple space dimensions in anisotropic media are 12 developed. Due to the anisotropy in the hydraulic conductivities of natural soils, the soil medium within which the 13 soi...

Scaling conditions to achieve self-similar solutions of 3-Dimensional (3D) Reynolds-Averaged Navier-Stokes Equations, as an initial and boundary value problem, are obtained by utilizing Lie Group of Point Scaling Transformations. By means of an open-source Navier-Stokes solver and the derived self-similarity conditions, we demonstrated self-similar...

Groundwater closely interacts with surface water and even climate systems in most hydroclimatic settings. Fractal scaling analysis of groundwater dynamics is of significance in modeling hydrological processes by considering potential temporal long-range dependence and scaling crossovers in the groundwater level fluctuations. In this study, it is de...

Using fractional calculus, a dimensionally consistent governing equation of transient, saturated groundwater flow in fractional time in a multi-fractional confined aquifer is developed. First, a dimensionally consistent continuity equation for transient saturated groundwater flow in fractional time and in a multi-fractional, multidimensional confin...

A lack of observations within watersheds can make the production of streamflow data via hydrologic models a big challenge. This study evaluates the model performance of the Watershed Environmental Hydrology Hydro-Climate Model (WEHY-HCM), reproducing streamflow in a sparsely gauged watershed. The fifth generation mesoscale model (MM5) is utilized w...

It is important to assess the reliability of high-resolution climate variables used as input to hydrologic models. High-resolution climate data is often obtained through the downscaling of Global Climate Models and/or historical reanalysis, depending on the application. In this study, the performance of dynamically downscaled precipitation from the...

The Saint-Venant equations are commonly used as the governing equations to solve for modeling the spatially varied unsteady flow in open channels. The presence of uncertainties in the channel or flow parameters renders these equations stochastic, thus requiring their solution in a stochastic framework in order to quantify the ensemble behavior and...

The characteristic form of the Saint–Venant equations was solved in a stochastic setting by using a newly proposed Fokker–Planck Equation (FPE) methodology. This methodology computes the ensemble behavior and variability of a system by directly solving for its time-space evolutionary probability distribution. The new methodology was tested on a sto...

The impacts of climate change on watershed-scale precipitation through the 21st century were investigated over eight study watersheds in Northern California based on dynamically downscaled CMIP5 future climate projections from three GCMs (CCSM4, HadGEM2-ES, and MIROC5) under the RCP4.5 and RCP8.5 future climate scenarios. After evaluating the model...

Extreme floods are regarded as one of the most catastrophic natural hazards and can result in significant morphological changes induced by pronounced sediment erosion and deposition processes over the landscape. However, the effects of extreme floods of different return intervals on the floodplain and river channel morphological evolution with the...

A dimensionally-consistent governing equation of transient, saturated groundwater flow in fractional time in a multi-fractional confined aquifer is developed. First, a continuity equation for transient groundwater flow in fractional time and in a multi-fractional, multi-dimensional confined aquifer is developed. An equation of water flux is also de...

Although fractional integration and differentiation have found many applications in various fields of science, such as physics, finance, bioengineering, continuum mechanics and hydrology, their engineering applications, especially in the field of fluid flow processes, are rather limited. In this study, a finite difference numerical approach is prop...

Estimating maximum precipitation (MP) over a watershed is a necessary process to estimate maximum flood which is used in the planning and design of dams. Major storms in Northern California are caused by so called atmospheric rivers (ARs), which are narrow, but rich moisture atmospheric flows from the tropics. To estimate the MP over the Shasta Dam...

As population and infrastructure continue to increase, our society has become more vulnerable to extreme events. Flood is an example of a hydro-meteorological disaster that has a strong societal impact. Tropical cyclones are recognized for their ability to generate intense precipitation that may in turn create disastrous floods. In the context of c...

Watershed Environmental Hydrology Hydro-Climate Model (WEHY-HCM) was used to simulate the surface flows of the Upper Middle Fork (UMF) Watershed under different climate conditions. Long-term historical atmospheric conditions over the Middle Fork Feather River Basin were reconstructed for the 63-year period between October 1950 and September 2013 by...

The physical upper bound of precipitation, referred to as the maximum precipitation (MP), was estimated over the American River Watershed in Northern California under future climate conditions by means of a physically-based regional atmospheric model. Severe storm events over ARW are mainly caused by an atmospheric river (AR) which is a high-moistu...