Modeling Flow,Nutrient, and Sediment Delivery from a Large International Watershed Using a Field‐Scale SWAT Model

A large international watershed, the St. Clair‐Detroit River System, containing both extensive urban and agricultural areas, was modeled using the Soil and Water Assessment Tool (SWAT) model. The watershed, located in southeastern Michigan, United States, and southwestern Ontario, Canada, encompasses the St. Clair, Clinton, Detroit (DT), Sydenham (SY), Upper, and Lower Thames subwatersheds. The SWAT input data and model resolution (i.e., hydrologic response units, HRUs), were established to mimic farm boundaries, the first time this has been done for a watershed of this size. The model was calibrated (2007–2015) and validated (2001–2006) with a mix of manual and automatic methods at six locations for flow and water quality at various time scales. The model was evaluated using Nash–Sutcliffe efficiency and percent bias and was used to explore major water quality issues. We showed the importance of allowing key parameters to vary among subwatersheds to improve goodness of fit, and the resulting parameters were consistent with subwatershed characteristics. Agricultural sources in the Thames and SY subwatersheds and point sources from DT subwatershed were major contributors of phosphorus. Spatial distribution of phosphorus yields at HRU and subbasin levels identified locations for potential management targeting for both point and nonpoint sources and revealed that in some subwatersheds nonpoint sources are dominated by urban sources.     

Yield and Water Productivity of Winter Wheat under Various Irrigation Capacities

The Agricultural Production Systems sIMulator model validated in a prior study for winter wheat was used to simulate yield, aboveground crop biomass (BM), transpiration (T), and evapotranspiration under four irrigation capacities (ICs) (0, 1.7, 2.5, and 5 mm/day) with two nitrogen (N) application rates (N1, 94 kg N/ha; N2, 160 kg N/ha) to (1) understand the performance of winter wheat under different ICs and (2) develop crop water production function under various ICs and N rates. Evaluation was based on yield, aboveground crop BM, transpiration productivity (TP), crop water productivity (WP), and irrigation WP (IWP). Simulation results showed winter wheat yield increased with increase in N application rate and IC. However, the rate of yield increase gradually reduced with additional irrigation beyond 2.5 mm/day. A 5 mm/day IC required a total of 190 mm irrigation and produced a 5%–16% yield advantage over 2.5 mm/day. This indicates it is possible to reduce groundwater use for wheat by 50% incurring only 5%–16% yield loss relative to 5 mm/day. The TP and IWP for grain were slightly higher under IC of 1.7 mm/day (15.2–16.1 kg/ha/mm and 0.98–1.6 kg/m³) when compared to 5 mm/day (14.7–15.5 kg/ha/mm and 0.6–1.06 kg/m³), respectively. Since TP and IWPs are relatively higher under lower ICs, winter wheat could be a suitable crop under lower ICs in the region. Relationship between yield–T and yield–ET was linear with a slope of 15–16 and 9.5–10 kg/ha/mm, respectively. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Evaluation of SWAT Impoundment Modeling Methods in Water and Sediment Simulations

Worldwide studies show 80%–90% of all sediments eroded from watersheds is trapped within river networks such as reservoirs, ponds, and wetlands. To represent the impact of impoundments on sediment routing in watershed modeling, Soil and Water Assessment Tool (SWAT) developers recommend to model reservoirs, ponds, and wetlands using impoundment tools (ITs). This study evaluates performance of SWAT ITs in the modeling of a small, agricultural watershed dominated by lakes and wetlands. The study demonstrates how to incorporate impoundments into the SWAT model, and discusses and evaluates involved parameters. The study then recommends an appropriate calibration sequence, i.e., landscape parameters calibration, followed by pond/wetlands calibration, then channel parameter calibrations, and lastly, reservoir parameter calibration. Results of this study demonstrate not following SWAT recommendation regarding modeling water land use as an impoundment depreciates SWAT performance, and may lead to misplaced calibration efforts and model over‐calibration. Further, the chosen method to model impoundments’ outflow significantly impacts sediment loads in the watershed, while streamflow simulation is not very sensitive. This study also allowed calculation of mass accumulation rates in modeled impoundments where the annual mass accumulation rate in wetlands (2.3 T/ha/yr) was 39% higher than mass accumulation rate in reservoirs (1.4 T/ha/yr).     

Modeling and simulation of biogas-fueled power system

The main objective of this paper is to develop a complete model that fully simulate a biogas-fueled power plant which can be used to supply a rural farm with sufficient electricity. The reactor is fed with animal manure of the farm. The proposed model consists of three main parts; a biogas reactor, a microturbine (MT) coupled to a permanent magnet synchronous generator, and a storage system. The model describes the dynamics of an MT and it is suitable for both steady state and transient simulation and analysis. The volume of biogas output delivered from the Anaerobic Digester depends on the reactor volume, reactor temperature, and animal manure type. The storage system is used to store the excess value of biogas if any. It is composed of two parts: a comparator and a storage tank. The comparator compares the volume of biogas produced by the reactor with that needed to supply the load. An adaptive controller is developed to withstand the system against any transient condition such as suddenly load increase/decrease. The proposed model is implemented for chemical and physical behaviors of the biogas production process, as well as for different variables of MT-generator operations. The model is implemented in Matlab/Simulink environment and tested under different operating conditions in both steady state and transient status to study the impacts of different variables on the system output. The output results prove its applicability and effectiveness under different operating conditions.     

A comprehensive approach to API RP 752 and 753 building siting studies

Facility siting studies are an important part of process safety, and are required for facilities that fall under OSHA’s PSM program. Facility siting is frequently interpreted as performing a building siting study which adheres to the guidance given in API RP 752. Building siting may also consider siting of temporary or portable buildings based on the guidance in API RP 753. While both API RP 752 and API RP 753 provide a framework and some guidance for performing building siting studies, they do not provide detailed methodologies or provide guidance on performing a detailed analysis. As a result many building siting studies are inconsistent in their overall approach, or in the way they address hazards. Due to the recent scrutiny applied to building siting studies, more attention has been given to provide evaluations which correctly describe the range of hazards that may affect an occupied building at a petrochemical facility. This paper outlines a comprehensive methodology for performing building siting studies at such facilities. The methodology addresses the applicable hazards and the available tools by which the potential impacts to building occupants can be evaluated.     

生物膜反应器进出水底物浓度相关性研究

从套氧生物膜反器,异养－好氧生物膜反应器和硝化生物膜反应器三方面,全面考察了进水底物浓度对生物膜反应器稳态出水水质的影响委现Ｓｅ随Ｓ０的变化呈现半Ｕ形曲线。在传统的线性模型基础上,提出了非线性Ｓｅ－Ｓ０的模型,该模型能很好地定量描述试验所得数据,并从的数据得到进一步的验证。     

居住区气温变化模型及应用

借助居住区热时间常数和地表热时间常数计算城市局地气温变化,给出的数学模型简单实用,但考虑了多项城市相关参数。结果表明实测值与预测值吻合较好。对部分城市参数作了敏感性分析,初步揭示了各参数变化对城市居住区气温的影响。     

基于无人机建模的尾矿库溃坝事故推演*

为诠释尾矿库溃坝后水砂演进过程,提升尾矿库事故灾害应急处置能力,采用无人机倾斜摄影技术获取尾矿库全息影像,建立尾矿库三维数字高程模型,导入三维流体计算软件对尾矿库进行溃坝事故推演。结果表明:尾矿库实景三维模型能高精度还原尾矿库实际情况,尾矿库溃坝将淹没库区临时厂房建筑及下游村落;其中,上游沟谷临时厂房建筑水位高程最大达8 m,尾砂淤积厚度最高达10.5 m,下游沟谷村落水位高程最大达10 m,尾砂淤积厚度最高达2.5 m;通过对库区下游布设监测点,得出各监测点处水位高程和尾砂淤积厚度变化规律,分析溃坝主要影响区域。研究结果可为尾矿库风险防控、应急响应工作提供借鉴。     

A CALIBRATION PROCEDURE USING TOPMODEL TO DETERMINE SUITABILITY FOR EVALUATING POTENTIAL CLIMATE CHANGE EFFECTS ON WATER YIELD1

ABSTRACT: An evaluation was conducted on three forested upland watersheds in the northeastern U.S. to test the suitability of TOPMODEL for predicting water yield over a wide range of climatic scenarios. The analysis provides insight of the usefulness of TOPMODEL as a predictive tool for future assessments of potential long-term changes in water yield as a result of changes in global climate. The evaluation was conducted by developing a calibration procedure to simulate a range of climatic extremes using historical temperature, precipitation, and streamfiow records for years having wet, average, and dry precipitation amounts from the Leading Ridge (Pennsylvania), Fernow (West Virginia), and Hubbard Brook (New Hampshire) Experimental Watersheds. This strategy was chosen to determine whether the model could be successfully calibrated over a broad range of soil moisture conditions with the assumption that this would be representative of the sensitivity necessary to predict changes in streamfiow under a variety of climate change scenarios. The model calibration was limited to a daily time step, yet performed reasonably well for each watershed. Model efficiency, a least squares measure of how well a model performs, averaged between 0.64 and 0.78. A simple test of the model whereby daily temperatures were increased by 1.7°C, resulted in annual water yield decreases of 4 to 15 percent on the three watersheds. Although these results makes the assumption that the model components adequately describe the system, this version of TOPMODEL is capable to predict water yield impacts given subtle changes in the temperature regime. This suggests that adequate representations of the effects of climate change on water yield for regional assessment purposes can be expected using the TOPMODEL concept.     

EVALUATION OF RUNOFF,EROSION, AND PHOSPHORUS MODELING SYSTEM—SIMPLE1

ABSTRACT: The purpose of this study was to evaluate the performance of Spatially Integrated Models for Phosphorus Loading and Erosion (SIMPLE) in predicting runoff volume, sediment loss, and phosphorus loading from two watersheds. The modeling system was applied to the 334 ha QOD subwatershed, part of the Owl Run watershed, located in Fauquier County, Virginia, and to the 2240 ha watershed, Battle Branch, located in Delaware County, Oklahoma. Simulation runs were conducted at cell and field scales, and simulation results were compared with observed data. Runoff volume and dissolved phosphorus loading were measured at the Battle Branch watershed. Runoff volume, sediment yield, and total phosphorus loading were measured at the QOD site. SIMPLE tended to underestimate runoff volumes during the dormant period, from November to March. The comparison between observed and predicted dissolved phosphorus showed better correlation than for observed and predicted total phosphorus loading. Cell level simulations provided similar estimates of runoff volume and phosphorus loading when compared to field level simulations for both watersheds. However, observed sediment yields better compared with the values predicted from the cell level simulation when compared to field level simulation. Finally, results of model evaluation indicated that SIMPLE's predictive ability is acceptable for screening applications but not for site-specific quantitative predictions.