Land-use dynamics in a southern Illinois (USA) watershed

The Cache River of southernmost Illinois is used as a case study for developing and demonstrating an approach to quantitatively link (1) national agricultural policy and global agricultural markets, (2) landowner's decisions on land use, (3) spatial patterns of land use at a watershed scale, and (4) hydrologic impacts, thus providing a basis to predict, under a certain set of circumstances, the environmental consequences of economic and political decisions made at larger spatial scales. The heart of the analysis is an estimation, using logistic regression, of the affect of crop prices and Conservation Reserve Program (CRP) rental rates on farmland owner's decisions whether to reenroll in the CRP or return to crop production. This analysis shows that reasonable ranges for crop prices (80%–150% of 1985–1995 values) and CRP rental rates (0–125% of 1985–1995 rates) result in a range of 3%–92% of CRP lands being returned to crop production, with crop prices having a slightly greater effect than CRP rental rates. Four crop price/CRP rental rate scenarios are used to display resulting land-use patterns, and their effect on sediment loads, a critical environmental quality parameter in this case, using the agricultural non point source (AGNPS) model. These scenarios demonstrate the importance of spatial pattern of land uses on hydrological and ecological processes within watersheds. The approach developed can be adapted for use by local governments and watershed associations whose goals are to improve watershed resources and environmental quality.     

Economic analysis of best management practices to reduce watershed phosphorus losses

In phosphorus-limited freshwater systems, small increases in phosphorus (P) concentrations can lead to eutrophication. To reduce P inputs to these systems, various environmental and agricultural agencies provide producers with incentives to implement best management practices (BMPs). In this study, we examine both the water quality and economic consequences of systematically protecting saturated, runoff-generating areas from active agriculture with selected BMPs. We also examine the joint water quality/economic impacts of these BMPs-specifically BMPs focusing on barnyards and buffer areas. Using the Variable Source Loading Function model (a modified Generalized Watershed Loading Function model) and net present value analysis (NPV), the results indicate that converting runoff-prone agricultural land to buffers and installing barnyard BMPs are both highly effective in decreasing dissolved P loss from a single-farm watershed, but are also costly for the producer. On average, including barnyard BMPs decreases the nutrient loading by about 5.5% compared with only implementing buffers. The annualized NPV for installing both buffers on only the wettest areas of the landscape and implementing barnyard BMPs becomes positive only if the BMPs lifetime exceeds 15 yr. The spatial location of the BMPs in relation to runoff producing areas, the time frame over which the BMPs are implemented, and the marginal costs of increasing buffer size were found to be the most critical considerations for water quality and profitability. The framework presented here incorporates estimations of nutrient loading reductions in the economic analysis, and is applicable to farms facing BMP adoption decisions.     

Multivariate analysis of paired watershed data to evaluate agricultural best management practice effects on stream water phosphorus

Quantification of the effects of management programs on water quality is critical to agencies responsible for water resource protection. This research documents reductions in stream water phosphorus (P) loads resulting from agricultural best management practices (BMPs) implemented as part of an effort to control eutrophication of Cannonsville Reservoir, a drinking water supply for New York City. Dairy farms in the upstate New York reservoir basin were the target of BMPs designed to reduce P losses. A paired watershed study was established on one of these farms in 1993 to evaluate changes in P loading attributable to implementation of BMPs that included manure management, rotational grazing, and improved infrastructure. Intensive stream water monitoring provided data to calculate P loads from the 160-ha farm watershed for all runoff events during a two-year pre-treatment period and a four-year post-treatment period. Statistical control for inter-annual climatic variability was provided by matched P loads from a nearby 86-ha forested watershed, and by several event flow variables measured at the farm. A sophisticated multivariate analysis of covariance (ANCOVA) provided estimates of both seasonal and overall load reductions. Statistical power and the minimum detectable treatment effect (MDTE) were also calculated. The results demonstrated overall event load reductions of 43% for total dissolved phosphorus (TDP) and 29% for particulate phosphorus (PP). Changes in farm management practices and physical infrastructure clearly produced decreases in event P losses measurable at the small watershed scale.     

The opportunity cost of regulating phosphorus from broiler production in the Illinois River Basin

The Illinois River Basin in eastern Oklahoma and northwest Arkansas is an example of a region where significant growth in poultry production has been accompanied by water quality problems. The primary concern in the basin is the problem of phosphorus in runoff that is associated with application of litter to crops. Existing data suggest that there has been a continuing decline in the quality of water in the Illinois River, and discussions have focused on developing and implementing a phosphorus standard. The specific objectives of this study are to estimate the reduction in poultry production necessary to achieve the reduction in phosphorus runoff under a set of phosphorus constraints, including soil test phosphorus, and to estimate the opportunity costs of reducing poultry production in the basin under each phosphorus constraint on the economic activity in the watershed. A mathematical programming model that incorporates poultry production and cropping decisions is developed. The parameters for the model are identified and then it is solved to provide a base solution. Model solutions are then developed for the different policy target levels of phosphorus. The model structure is modified to account for the presence of soil test phosphorus levels and the corresponding limits on soil test phosphorus throughout the basin. This formulation includes current soil test phosphorus throughout the basin. All of the applications assume that the only disposal option for poultry litter is land application within the basin. An economic impact assessment of the effects of phosphorus limitations in the basin is also conducted for Arkansas counties only, Oklahoma counties only, and all five affected counties combined.     

Soil phosphorus, management practices, and their relationship to phosphorus delivery in the Iowa Clear Lake agricultural watershed

Clear Lake is on Iowa's list of impaired water bodies because of high P concentration. This study assessed soil-test phosphorus (STP), management practices, and P loads from its agricultural watershed. Management practice histories and STP for eight basins were surveyed in 1999. Soil samples (15-cm depth) were analyzed for STP with agronomic [Bray P1 (BP), Olsen (OP), Mehlich 3 (M3P) and environmental [iron oxide-impregnated paper (FeP) and water extraction (WP)] tests. Total phosphorus (TP) concentrations in water discharge from five basins were measured during two years, and TP loads were measured for two basins. The agronomic P tests showed that 46 to 83% (depending on the test) of the area tested above optimum for crops. Correlations among tests were high for OP, M3P, and FeP (r > 0.96) and lower for BP and WP (r = 0.88-0.93). Moldboard- and chisel-plow tillage predominated (82% of the area). Applied P (mainly fertilizer) averaged 15 kg P ha(-1) yr(-1), and 40% of the high-testing area (M3P test) was being fertilized. The mean annual water TP concentration across five basins was 275 to 474 microg L(-1). The two-year mean TP loads for the two gauged basins were 1504 and 1510 g P ha(-1) yr(-1). Water TP concentration increased linearly with increasing STP. Relationships were stronger for M3P and FeP (R2 = 0.96-0.97 for annual means and 0.77-0.79 for storm-flow events) than for BP or WP (R2 = 0.88-0.91 and 0.59-0.69, respectively). Improving P and soil conservation practices in high-testing areas could reduce P loads to the lake.     

Evaluating agricultural best management practices in tile-drained subwatersheds of the Mackinaw River, Illinois

Best management practices (BMPs) are widely promoted in agricultural watersheds as a means of improving water quality and ameliorating altered hydrology. We used a paired watershed approach to evaluate whether focused outreach could increase BMP implementation rates and whether BMPs could induce watershed-scale (4000 ha) changes in nutrients, suspended sediment concentrations, or hydrology in an agricultural watershed in central Illinois. Land use was >90% row crop agriculture with extensive subsurface tile drainage. Outreach successfully increased BMP implementation rates for grassed waterways, stream buffers, and strip-tillage within the treatment watershed, which are designed to reduce surface runoff and soil erosion. No significant changes in nitrate-nitrogen (NO-N), total phosphorus (TP), dissolved reactive phosphorus, total suspended sediment (TSS), or hydrology were observed after implementation of these BMPs over 7 yr of monitoring. Annual NO-N export (39-299 Mg) in the two watersheds was equally exported during baseflow and stormflow. Mean annual TP export was similar between the watersheds (3.8 Mg) and was greater for TSS in the treatment (1626 ± 497 Mg) than in the reference (940 ± 327 Mg) watershed. Export of TP and TSS was primarily due to stormflow (>85%). Results suggest that the BMPs established during this study were not adequate to override nutrient export from subsurface drainage tiles. Conservation planning in tile-drained agricultural watersheds will require a combination of surface-water BMPs and conservation practices that intercept and retain subsurface agricultural runoff. Our study emphasizes the need to measure conservation outcomes and not just implementation rates of conservation practices.     

Multi-scale analysis of oxygen demand trends in an urbanizing Oregon watershed, USA

Human alteration of the landscape has an extensive influence on the biogeochemical processes that drive oxygen cycling in streams. We estimated trends from the mid-1990s to 2003, using the seasonal Mann-Kendall's test, for percent saturation dissolved oxygen (DO), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and ammonia-nitrogen (NH(3)-N) for 12 sites in the Rock Creek watershed, northwest Oregon, USA. In order to understand the influence of landscape change, scale, and stormwater runoff management on dissolved oxygen trends, we calculated land cover change through aerial photo interpretation at full-basin, local (near sample point) basin, and 100m stream buffer scales, for the years 1994 and 2000. Significant (p < or = 0.05) trends occurred in DO (increasing at five sites), COD (decreasing at seven sites), TKN (decreasing at five sites, increasing at one site), and NH(3)-N (decreasing at one site, increasing at one site). Significant land cover change occurred in agricultural land cover (-8% for the entire basin area) and residential land cover (+10% for the entire basin area) (p < or = 0.05). Correlation results indicated that: (1) forest cover negatively influenced COD at the full basin scale and positively influences NH(3)-N at local scales, (2) residential land cover influenced oxygen demand variables at local scales, (3) agricultural land cover did not influence oxygen demand, (4) local topography negatively influenced TKN and NH(3)-N, and (5) stormwater runoff management infrastructure correlated positively with COD at the local scale. This study indicates that landscape factors influencing DO conditions for the study streams act at multiple scales, suggesting that better knowledge of scale-process interactions can guide watershed managers' decision making in order to maintain improving water quality conditions.     

Evaluation of the ADAPT model for simulating nitrogen dynamics in a tile-drained agricultural watershed in central Illinois

Assessing the accuracy of agronomic and water quality simulation models in different soils, land-use systems, and environments provides a basis for using and improving these models. We evaluated the performance of the ADAPT model for simulating riverine nitrate-nitrogen (NO3-N) export from a 1500-km2 watershed in central Illinois, where approximately 85% of the land is used for maize-soybean production and tile drainage is common. Soil chemical properties, crop nitrogen (N) uptake coefficient, dry matter ratio, and a denitrification reduction coefficient were used as calibration parameters to optimize the fit between measured and simulated NO3-N load from the watershed for the 1989 to 1993 period. The applicability of the calibrated parameter values was tested by using these values for simulating the 1994 to 1997 period on the same watershed. Willmott's index of agreement ranged from 0.91 to 0.97 for daily, weekly, monthly, and annual comparisons of riverine nitrate N loads. Simulation accuracy generally decreased as the time interval decreased. Willmott's index for simulated crop yields ranged from 0.91 to 0.99; however, observed crop yields were used as input to the model. The partial N budget results suggested that 52 to 72 kg N ha(-1) yr(-1) accumulated in the soil, but simulated biological N fixation associated with soybeans was considerably greater than literature values for the region. Improvement of the N fixation algorithms and incorporation of mechanisms that describe soybean yield in response to environmental conditions appear to be needed to improve the performance of the model.     

Isotopic evidence of nitrate sources and denitrification in the Mississippi River, Illinois

Anthropogenic nitrate (NO3-) within the Mississippi-Atchafalaya River basin and discharge to the Gulf of Mexico has been linked to serious environmental problems. The sources of this NO3- have been estimated by others using mass balance methods; however, there is considerable uncertainty in these estimates. Part of the uncertainty is the degree of denitrification that the NO3- has undergone. The isotopic composition of NO3- in the Mississippi River adjacent to Illinois and tile drain (subsurface drain) discharge in agricultural areas of east-central Illinois was examined using N and O isotopes to help identify the major sources of NO3- and assess the degree of denitrification in the samples. The isotopic evidence suggests that most of the NO3- in the river is primarily derived from synthetic fertilizers and soil organic N, which is consistent with published estimates of N inputs to the Mississippi River. The 1:2 relationship between delta18O and delta15N also indicate that, depending on sample location and season, NO3- in the river and tile drains has undergone significant denitrification, ranging from about 0 to 55%. The majority of the denitrification appears to have occurred before discharge into the Mississippi River.     

Respective contributions of point and non-point sources of E. coli and enterococci in a large urbanized watershed (the Seine river, France)

Because the large rivers of the Seine watershed have a low microbiological water quality, the main sources of fecal contamination were investigated in the present study. The inputs of the point (wastewater treatment plants (WWTPs) effluents) and non-point sources (surface runoff and soil leaching) of fecal bacteria were quantified for Escherichia coli and intestinal enteroccoci used as bacterial indicators. In order to assess the contamination through non-point sources, fecal indicators abundance was estimated in samples collected in small streams located in rural areas upstream from all point sources; these small rivers were characterized by the land use of their watershed. Bacterial indicator numbers were also measured in effluents of WWTPs, some using classical treatment (settling followed by activated sludge process) and some using an additional disinfection stage (UV irradiation). These data were used to estimate the respective importance of each type of source at the scale of the whole Seine river watershed taking into account the land use and the population density. It shows the predominant importance of the point sources of fecal indicator bacteria at the scale of the whole watershed. In a scenario in which activated sludge treatment would be complemented with UV in all WWTPs located in this watershed, the non-point sources of fecal indicator bacteria would be dominant.     

The effects of multiple beneficial management practices on hydrology and nutrient losses in a small watershed in the Canadian prairies

Most beneficial management practices (BMPs) recommended for reducing nutrient losses from agricultural land have been established and tested in temperate and humid regions. Previous studies on the effects of these BMPs in cold-climate regions, especially at the small watershed scale, are rare. In this study, runoff and water quality were monitored from 1999 to 2008 at the outlets of two subwatersheds in the South Tobacco Creek watershed in Manitoba, Canada. Five BMPs-a holding pond below a beef cattle overwintering feedlot, riparian zone and grassed waterway management, grazing restriction, perennial forage conversion, and nutrient management-were implemented in one of these two subwatersheds beginning in 2005. We determined that >80% of the N and P in runoff at the outlets of the two subwatersheds were lost in dissolved forms, ≈ 50% during snowmelt events and ≈ 33% during rainfall events. When all snowmelt- and rainfall-induced runoff events were considered, the five BMPs collectively decreased total N (TN) and total P (TP) exports in runoff at the treatment subwatershed outlet by 41 and 38%, respectively. The corresponding reductions in flow-weighted mean concentrations (FWMCs) were 43% for TN and 32% for TP. In most cases, similar reductions in exports and FWMCs were measured for both dissolved and particulate forms of N and P, and during both rainfall and snowmelt-induced runoff events. Indirect assessment suggests that retention of nutrients in the holding pond could account for as much as 63 and 57%, respectively, of the BMP-induced reductions in TN and TP exports at the treatment subwatershed outlet. The nutrient management BMP was estimated to have reduced N and P inputs on land by 36 and 59%, respectively, in part due to the lower rates of nutrient application to fields converted from annual crop to perennial forage. Overall, even though the proportional contributions of individual BMPs were not directly measured in this study, the collective reduction of nutrient losses from the five BMPs was substantial.     

Bathymetric and core analysis of the Latrobe River delta to assist in catchment management

In this study, an analysis of bathymetric surveys of the Latrobe River delta conducted in 1879 and 1992 is combined with pollen analysis of cores from the delta sediments to assist in setting management priorities for the Latrobe River catchment, a 5000 km²catchment in the south-east of Australia. Reconstructed delta surfaces from 1879 (not long after European settlement of the area) and 1992 were compared to quantify areas of net erosion and deposition. These were compared to post-European deposition depths determined by the presence of exotic pollen species in the sediment. The results indicated that: (1) average sedimentation rates in the receiving lake for the Latrobe River are less than 1 mm yr⁻¹; (2) the deposited material is fine with no material considered as bedload; and (3) the fine nature of the deposited material makes it suitable for carrying a large load of nutrients. These results created a shift in management focus from concern over sedimentation and erosion in general to a greater emphasis on nutrients. While the integrated management of catchments is implicitly contemporary, it should always be performed within a historical context. Failure to do this can lead to management priorities that do not concur with the facts of catchment response and can therefore result in inefficient resource allocation. The use of studies which provide a historical perspective on the problem are therefore critical.     

Lability of drinking water treatment residuals (WTR) immobilized phosphorus: aging and pH effects

Time constraints associated with conducting long-term (>20 yr) field experiments to test the stability of drinking water treatment residuals (WTR) sorbed phosphorus (P) inhibit improved understanding of the fate of sorbed P in soils when important soil properties (e.g., pH) change. We used artificially aged samples to evaluate aging and pH effects on lability of WTR-immobilized P. Artificial aging was achieved through incubation at elevated temperatures (46 or 70 degrees C) for 4.5 yr, and through repeated wetting and drying for 2 yr. Using a modified isotopic ((32)P) dilution technique, coupled with a stepwise acidification procedure, we monitored changes in labile P concentrations over time. This technique enabled evaluation of the effect of pH on the lability of WTR-immobilized P. Within the pH range of 4 to 7, WTR amendment, coupled with artificial aging, ultimately reduced labile P concentrations by > or = 75% relative to the control (no-WTR) samples. Soil samples with different physicochemical properties from two 7.5-yr-old, one-time WTR-amended field sites were utilized to validate the trends observed with the artificially aged samples. Despite the differences in physicochemical properties among the three (two field-aged and one artificially aged) soil samples, similar trends of aging and pH effects on lability of WTR-immobilized P were observed. Labile P concentrations of the WTR-amended field-aged samples of the two sites decreased 6 mo after WTR amendment and the reduction persisted for 7.5 yr, ultimately resulting in > or = 70% reduction, compared to the control plots. We conclude that WTR application is capable of reducing labile P concentration in P-impacted soils, doing so for a long time, and that within the commonly encountered range of pH values for agricultural soils WTR-immobilized P should be stable.     

Grazing management effects on sediment, phosphorus, and pathogen loading of streams in cool-season grass pastures

Erosion and runoff from pastures may lead to degradation of surface water. A 2-yr grazing study was conducted to quantify the effects of grazing management on sediment, phosphorus (P), and pathogen loading of streams in cool-season grass pastures. Six adjoining 12.1-ha pastures bisected by a stream in central Iowa were divided into three treatments: continuous stocking with unrestricted stream access (CSU), continuous stocking with restricted stream access (CSR), and rotational stocking (RS). Rainfall simulations on stream banks resulted in greater ( < 0.10) proportions of applied precipitation and amounts of sediment and P transported in runoff from bare sites than from vegetated sites across grazing treatments. Similar differences were observed comparing vegetated sites in CSU and RS pastures with vegetated sites in CSR pastures. Bovine enterovirus was shed by an average of 24.3% of cows during the study period and was collected in the runoff of 8.3 and 16.7% of runoff simulations on bare sites in CSU pastures in June and October of 2008, respectively, and from 8.3% of runoff simulations on vegetated sites in CSU pastures in April 2009. Fecal pathogens (bovine coronavirus [BCV], bovine rotavirus group A, and O157:H7) shed or detected in runoff were almost nonexistent; only BCV was detected in feces of one cow in August of 2008. Erosion of cut-banks was the greatest contributor of sediment and P loading to the stream; contributions from surface runoff and grazing animals were considerably less and were minimized by grazing management practices that reduced congregation of cattle by pasture streams.     

Quantifying phosphorus retention and release in rivers and watersheds using extended end-member mixing analysis (E-EMMA)

Extended end-member mixing analysis (E-EMMA) is presented as a novel empirical method for exploring phosphorus (P) retention and release in rivers and watersheds, as an aid to water-quality management. E-EMMA offers a simple and versatile tool that relies solely on routinely measured P concentration and flow data. E-EMMA was applied to two river systems: the Thames (U.K.) and Sandusky River (U.S.), which drain similar watershed areas but have contrasting dominant P sources and hydrology. For both the Thames and Sandusky, P fluxes at the watershed outlets were strongly influenced by processes that retain and cycle P. However, patterns of P retention were markedly different for the two rivers, linked to differences in P sources and speciation, hydrology and land use. On an annual timescale, up to 48% of the P flux was retained for the Sandusky and up to 14% for the Thames. Under ecologically critical low-flow periods, up to 93% of the P flux was retained for the Sandusky and up to 42% for the Thames. In the main River Thames and the Sandusky River, in-stream processes under low flows were capable of regulating the delivery of P and modifying the timing of delivery in a way that may help to reduce ecological impacts to downstream river reaches, by reducing ambient P concentrations at times of greatest river eutrophication risk. The results also suggest that by moving toward cleaner rivers and improved ecosystem health, the efficiency of P retention may actually increase.     

长江、黄河上游汛期多雨时段变化的初步分析

利用具有代表性的两个气象站汛期降水资料进行初步分析得出,黄河上游各月多雨时段出现的旬序数均有提前的趋势,尤其7月份更加明显;通天河流域各月多雨时段出现的旬序数8月变化不明显,6月偏后、7月提前。     

Cascading ecological effects of low-level phosphorus enrichment in the Florida everglades

Few studies have examined long-term ecological effects of sustained low-level nutrient enhancement on wetland biota. To determine sustained effects of phosphorus (P) addition on Everglades marshes we added P at low levels (5, 15, and 30 microg L(-1) above ambient) for 5 yr to triplicate 100-m flow-through channels in pristine marsh. A cascade of ecological responses occurred in similar sequence among treatments. Although the rate of change increased with dosing level, treatments converged to similar enriched endpoints, characterized most notably by a doubling of plant biomass and elimination of native, calcareous periphyton mats. The full sequence of biological changes occurred without an increase in water total P concentration, which remained near ambient levels until Year 5. This study indicates that Everglades marshes have a near-zero assimilative capacity for P without a state change, that ecosystem responses to enrichment accumulate over time, and that downstream P transport mainly occurs through biota rather than the water column.     

A spatial analysis of phosphorus in the Mississippi river basin

Phosphorus (P) in rivers in the Mississippi River basin (MRB) contributes to hypoxia in the Gulf of Mexico and impairs local water quality. We analyzed the spatial pattern of P in the MRB to determine the counties with the greatest January to June P riverine yields and the most critical factors related to this P loss. Using a database of P inputs and landscape characteristics from 1997 through 2006 for each county in the MRB, we created regression models relating riverine total P (TP), dissolved reactive P (DRP), and particulate P (PP) yields for watersheds within the MRB to these factors. Riverine yields of P were estimated from the average concentration of each form of P during January to June for the 10-yr period, multiplied by the average daily flow, and then summed for the 6-mo period. The fraction of land planted in crops, human consumption of P, and precipitation were found to best predict TP yields with a spatial error regression model ( = 0.48, = 101). Dissolved reactive P yields were predicted by fertilizer P inputs, human consumption of P, and precipitation in a multiple regression model ( = 0.42, = 73), whereas PP yields were explained by crop fraction, human consumption of P, and soil bulk density in a spatial error regression model ( = 0.49, = 61). Overall, the Upper Midwest's Cornbelt region and lower Mississippi basin had the counties with the greatest P yields. These results help to point out specific areas where agricultural conservation practices that reduce losses to streams and rivers and point source P removal might limit the intensity or spatial occurrence of Gulf of Mexico hypoxia and improve local water quality.     

Collaborative environmental planning in river management: an application of multicriteria decision analysis in the White River Watershed in Vermont

Multicriteria decision analysis (MCDA) provides a well-established family of decision tools to aid stakeholder groups in arriving at collective decisions. MCDA can also function as a framework for the social learning process, serving as an educational aid in decision problems characterized by a high level of public participation. In this paper, the framework and results of a structured decision process using the outranking MCDA methodology preference ranking organization method of enrichment evaluation (PROMETHEE) are presented. PROMETHEE is used to frame multi-stakeholder discussions of river management alternatives for the Upper White River of Central Vermont, in the northeastern United States. Stakeholders met over 10 months to create a shared vision of an ideal river and its services to communities, develop a list of criteria by which to evaluate river management alternatives, and elicit preferences to rank and compare individual and group preferences. The MCDA procedure helped to frame a group process that made stakeholder preferences explicit and substantive discussions about long-term river management possible.