Soni M. Pradhanang

Evaluating Satellite Products for Precipitation Estimation in Mountain Regions: A Case Study for Nepal

Precipitation in mountain regions is often highly variable and poorly observed, limiting abilities to manage water resource challenges. Here, we evaluate remote sensing and ground station-based gridded precipitation products over Nepal against weather station precipitation observations on a monthly timescale. We find that the Tropical Rainfall Measuring Mission (TRMM) 3B-43 precipitation product exhibits little mean bias and reasonable skill in giving precipitation over Nepal. Compared to station observations, the TRMM precipitation product showed an overall Nash-Sutcliffe efficiency of 0.49, which is similar to the skill of the gridded station-based product Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE). The other satellite precipitation products considered (Global Satellite Mapping of Precipitation (GSMaP), the Climate Prediction Center Morphing technique (CMORPH), Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS)) were less skillful, as judged by Nash-Sutcliffe efficiency, and, on average, substantially underestimated precipitation compared to station observations, despite their, in some cases, higher nominal spatial resolution compared to TRMM. None of the products fully captured the dependence of mean precipitation on elevation seen in the station observations. Overall, the TRMM product is promising for use in water resources applications.

High-frequency dissolved organic carbon and nitrate measurements reveal differences in storm hysteresis and loading in relation to land cover and seasonality

Storm events dominate riverine loads of dissolved organic carbon (DOC) and nitrate, and are expected to increase in frequency and intensity in many regions due to climate change. We deployed three high-frequency (15-minute) in-situ absorbance spectrophotometers to monitor DOC and nitrate concentration for 126 storms in three watersheds with agricultural, urban, and forested land use/land cover. We examined intrastorm hysteresis and the influences of seasonality, antecedent conditions, storm size, and dominant land use/land cover on storm DOC and nitrate loads. DOC hysteresis was generally anti-clockwise at all sites, indicating distal and plentiful sources for all three streams despite varied DOC character and sources. Nitrate hysteresis was generally clockwise for urban and forested sites, but anti-clockwise for the agricultural site, indicating an exhaustible, proximal source of nitrate in the urban and forested sites, and more distal and plentiful sources of nitrate in the agricultural site. The agricultural site had significantly higher storm nitrate yield per water yield and higher storm DOC yield per water yield than the urban or forested sites. Seasonal effects were important for storm nitrate yield in all three watersheds and farm management practices likely caused complex interactions with seasonality at the agricultural site. Hysteresis indices did not improve predictions of storm nitrate yields at any site. We discuss key lessons from using high-frequency in-situ optical sensors.

The impact of information on behavior under an ambient-based policy for regulating nonpoint source pollution

[The impact of information on behavior under an ambient-based policy for regulating nonpoint source pollution] Haoran Miao, Jacob Fooks, Todd Guilfoos, Kent Messer, Soni M. Pradhanang, Jordan Suter, Simona Trandafir, Emi Uchida 1 Department of Environmental and Natural Resource Economics, University of Rhode Island 2 USDA Economics Research Service 3 Department of Applied Economics and Statistics, University of Delaware 4 Department of Geosciences, University of Rhode Island 5 Department of Agricultural and Resource Economics, Colorado State University * Corresponding Author. Email: haoran_miao@my.uri.edu. Kingston Coastal Institute, 1 Greenhouse Road, University of Rhode Island, Kingston, RI 02881.

Assessing the impact of urbanization on flood risk and severity for the Pawtuxet watershed, Rhode Island

ABSTRACT Campbell A, Pradhanang SM, Kouhi Anbaran S, Sargent J, Palmer Z, Audette M. 2017. Assessing the impact of urbanization on flood risk and severity for the Pawtuxet watershed, Rhode Island. Lake Reserv Manage. 34:74–87. This study models the Pawtuxet River watershed with the Soil and Water Assessment Tool (SWAT) and high spell analysis to understand the impacts of land use and management on flood events. The watershed is in central Rhode Island and contains the Scituate Reservoir and the southern suburbs of Providence. The area is divided between urban development along Narragansett Bay and forested land cover around the Scituate Reservoir. The model was calibrated and validated to a daily time step. The calibration data was for the entirety of 2010 including a flood event in March and early April, which caused significant damage to the region. The calibrated model had a Nash–Sutcliffe efficiency (NSE) of 0.69. The validation had an NSE of 0.65. The model was run with 3 land use/land cover scenarios: the 2011 statewide LULC as a baseline, increased urbanization around Narragansett Bay, and increased urbanization surrounding the reservoir. In the 2011 model, urban land cover accounted for only 13.49% of the study area. Simulated sub-daily flow for the watershed, at a 5 min time step, was used to understand the potential impact of urbanization on flood events. Each year from 2010 to 2013 was analyzed with high spell analysis; the average high spell volume in 2010 was nearly double all other years. The scenarios with increased urban land use saw an increase in the mean volume of high spells, however there was not an increase in the 2010 floods peak.