‘No net loss’ is a buzz phrase in environmental policy. Applied to a multitude of environmental targets such as biodiversity, wetlands and land productive capacity, no net loss (NNL) and related goals have been adopted by multiple countries and organizations, but these goals often lack clear reference scenarios: no net loss compared to what? Here, we examine policies with NNL and related goals, and identify three main forms of reference scenario. We categorize NNL policies as relating either to overarching policy goals, or to responses to specific impacts. We explore how to resolve conflicts between overarching and impact-specific NNL policies, and improve transparency about what NNL-type policies are actually designed to achieve.

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The many meanings of no net loss in environmental policy

Land-use changes and check dams reducing runoff and sediment yield on the Loess Plateau of China.

Extensive time and financial resources have been dedicated to address nonpoint sources of nitrogen and phosphorus in watersheds. Despite these efforts, many watersheds have not seen substantial improvement in water quality. The objective of this study is to review the literature and investigate key factors affecting the lack of improvement in nutrient levels in waterways in urban and agricultural regions. From 94 studies identified in the academic literature, we found that, although 60% of studies found improvements in water quality after implementation of Best Management Practices (BMPs) within the watershed, these studies were mostly modeling studies rather than field monitoring studies. For studies that were unable to find improvements in water quality after the implementation of BMPs, the lack of improvement was attributed to lack of knowledge about BMP functioning, lag times, nonoptimal placement and distribution of BMPs in the watershed, postimplementation BMP failure, and socio-political and economic challenges. We refer to these limiting factors as known unknowns. We also acknowledge the existence of unknown unknowns that hinder further improvement in BMP effectiveness and suggest that machine learning, approaches from the field of business and operations management, and long-term convergent studies could be used to resolve these unknown unknowns.

Best Management Practices for Diffuse Nutrient Pollution: Wicked Problems across Urban and Agricultural Watersheds

The intensive study of an individual watershed is required to develop effective and efficient watershed management plans. Identification of critical erosion-prone areas of the watershed and implementation of best management practices (BMPs) is necessary to control the watershed degradation by reducing the sediment and nutrient losses. The present study evaluates and recommends the BMPs in an agriculture-based Marol watershed (5092 km2) of India, using a hydrologic model, Soil and Water Assessment Tool (SWAT). After successful calibration and validation, the model simulated daily/monthly discharge and sediment were found satisfactory throughout the simulation period. The model was then applied with a calibrated set of parameters for evaluating the effectiveness of various management practices for sediment and nutrient loss control. Keeping in mind the existing agricultural practices, socio-economic aspects and geography of the study area, the management practices were focused on four crops (Maize, Rice, Soybeans and Ground nut), three fertilization levels (high, medium and low), four tillage treatments (Field cultivator, Conservation tillage, Zero tillage and Mould board plough), and two conservation operations (Contour farming and Filter strips). The simulated annual average sediment yield from the watershed was found to be 12.2 t.ha−1yr−1. The water balance analysis revealed that, the evapo-transpiration is predominant over the watershed (approximately 46.3% of the annual average rainfall). Reduction in sediment yield and nutrient loss was observed with alternate cropping treatments of Groundnut and Soybean, as compared to Paddy and Maize cultivation. Overall, based on simulated results, the field cultivator tillage practice and conservation practices viz., contour farming and filter strips, could be adopted to reduce sediment yield and nutrient losses in the critical sub-watersheds of the study area and in other watersheds with similar hydro-climatic conditions.

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Evaluation of best management practices for sediment and nutrient loss control using SWAT model

evaluating the effectiveness of postfire rehabilitation treatments is available in our digital library an online access to it is set as public so you can download it instantly. Our books collection saves in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the evaluating the effectiveness of postfire rehabilitation treatments is universally compatible with any devices to read.

Evaluating The Effectiveness Of Postfire Rehabilitation Treatments

Within river basins, water resources competition often exists between agricultural, municipal and industrial sectors, particularly in semi-arid regions where surface water and groundwater are managed conjunctively to sustain urban areas and food production. There is a need for physically-based modeling tools to assist with identifying successful water management strategies in these basins. This paper presents an updated version of SWAT-MODFLOW that allows application to large agro-urban river basins in semi-arid regions. Code changes include linkage between MODFLOW pumping cells and SWAT HRUs for groundwater irrigation, joint groundwater and surface water irrigation routines, and the use of MODFLOW-PSB to handle the large array of groundwater sources/sinks that exist in a highly managed river basin. Model performance is demonstrated for the 72,000 km2 South Platte River Basin, Colorado, USA. The model can be used in agro-urban river basins worldwide to assess water resources supply under a variety of scenarios.

Coupled SWAT-MODFLOW model for large-scale mixed agro-urban river basins

Characterization of the vulnerability of water bodies to pollution from natural and anthropogenic sources requires understanding the relationship between land use and water quality. This study aims (i) to explore the influence of upstream land use on annual stream water concentrations and loads of total nitrogen (TN) and phosphorus (TP) and (ii) to characterize the vulnerability of water bodies to TN and TP pollution as a function of land use under varying climatic conditions. Multiple linear regression models were used across 23 stream locations within the Jordan Lake watershed in North Carolina between 1992 and 2012 to explore land use-water quality relationships. The percentage of urban land use and wastewater treatment plant capacity were the most important factors with strong ( 0.7) and significant ( < 0.01) positive correlations with annual TN and TP concentrations and loads. Percent agricultural land was negatively correlated with TN in 18 out of 21 yr of the study period. Using analysis of covariance, significant ( 0.01) differences were determined between models developed for urban land use with TN and TP loads based on annual precipitation. Using concentrations instead of loads resulted in a nonsignificant difference between models for average and wet years. Finally, a procedure was developed to characterize the vulnerability to TN and TP pollution, computed as the probability of exceeding the nutrient standard limits. Results indicated that the vulnerability to TN and TP was controlled primarily by urban land use, with higher values in dry years than normal and wet years.

The Relationship between Land Use and Vulnerability to Nitrogen and Phosphorus Pollution in an Urban Watershed.

A probabilistic appraisal of rainfall-runoff modeling approaches within SWAT in mixed land use watersheds

. This study aims to understand the hydrologic responses to wildfires in
mountainous regions at various spatial scales. The Soil and Water Assessment
Tool (SWAT) was used to evaluate the hydrologic responses of the upper Cache la
Poudre Watershed in Colorado to the 2012 High Park and Hewlett wildfire
events. A baseline SWAT model was established to simulate the hydrology of
the study area between the years 2000 and 2014. A procedure involving land
use and curve number updating was implemented to assess the effects of
wildfires. Application of the proposed procedure provides the ability to
simulate the hydrologic response to wildfires seamlessly through mimicking
the dynamic of the changes due to wildfires. The wildfire effects on curve
numbers were determined comparing the probability distribution of curve
numbers after calibrating the model for pre- and post-wildfire conditions.
Daily calibration and testing of the model produced “very good” results.
No-wildfire and wildfire scenarios were created and compared to quantify
changes in average annual total runoff volume, water budgets, and full
streamflow statistics at different spatial scales. At the watershed scale,
wildfire conditions showed little impact on the hydrologic responses.
However, a runoff increase up to 75 % was observed between the scenarios in
sub-watersheds with high burn intensity. Generally, higher surface runoff and
decreased subsurface flow were observed under post-wildfire conditions.
Flow duration curves developed for burned sub-watersheds using full
streamflow statistics showed that less frequent streamflows become greater in
magnitude. A linear regression model was developed to assess the relationship
between percent burned area and runoff increase in Cache la Poudre Watershed.
A strong ( R2 >  0.8) and significant ( p  0.001) positive
correlation was determined between runoff increase and percentage of burned
area upstream. This study showed that the effects of wildfires on hydrology
of a watershed are scale-dependent. Also, using full streamflow statistics
through application of flow duration curves revealed that the wildfires had a
higher effect on peak flows, which may increase the risk of flash floods in
post-wildfire conditions.

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Assessing the hydrologic response to wildfires in mountainous regions

The Soil and Water Assessment Tool (SWAT) is a well-established modeling tool for simulating hydrologic processes in watershed systems. However, SWAT often does not perform well in highly m...

Ali Tasdighi

Papers

Coupled SWAT-MODFLOW model for large-scale mixed agro-urban river basins

The Relationship between Land Use and Vulnerability to Nitrogen and Phosphorus Pollution in an Urban Watershed.

A probabilistic appraisal of rainfall-runoff modeling approaches within SWAT in mixed land use watersheds

Assessing the hydrologic response to wildfires in mountainous regions

Using the SWAT Model in Intensively Managed Irrigated Watersheds: Model Modification and Application