Relating Land Use/Cover and Landscape Pattern to the Water Quality under the Simulation of SWAT in a Reservoir Basin, Southeast China

Understanding the relationship between land use/cover pattern and water quality could provide guidelines for non-point source pollution and facilitate sustainable development. The previous studies mainly relate the land use/cover of the entire region to the water quality at the monitoring sites, but the water quality at monitoring sites did not totally reflect the water environment of the entire basin. In this study, the land use/cover was monitored on Google Earth Engine in Tang-Pu Reservoir basin, China. In order to reflect the water quality of the whole study area, the spatial distribution of the determinants for water quality there, i.e., the total nitrogen and total phosphorus (TN&TP), were simulated by the Soil and Water Assessment Tool (SWAT). The redundancy analysis explored the correlations between land use/cover pattern and simulated TN&TP. The results showed that: (1) From 2009 to 2019, forest was the dominant land cover, and there was little land use/cover change. The landscape fragmentation increased, and the connectivity decreased. (2) About 25% TP concentrations and nearly all the TN concentrations at the monitoring points did not reach drinking water standard, which means nitrogen and phosphorus pollution were the most serious problems. The highest output per unit TN&TP simulated by SWAT were 44.50 kg/hm2 and 9.51 kg/hm2 and occurred in areas with highly fragile landscape patterns. (3) TN&TP correlated positively with cultivated and construction land but negatively with forest. The correlation between forest and TN&TP summited at 500–700-m buffer and construction land at 100-m buffer. As the buffer size increased, the correlation between the cultivated land, and the TN weakened, while the correlation with the TP increased. TN&TP correlated positively with the Shannon’s Diversity Index and negatively with the Contagion Index. This study provides a new perspective for exporting the impact of land use/cover pattern on water quality.

The assessment of the impact of short-term land use/cover changes on water resources in the Yanghe reservoir basin, China

Land Use/Land Cover (LULC) is the main factor that affects the hydrological process of catchment. A better understanding of its influence is of great significance to future land use planning and water resources management. Since 2011, the local government has implemented the land remediation plan, and the LULC has undergone major changes in the Yanghe Reservoir Basin. This paper used The Soil and Water Assessment Tool (SWAT) model to study the Blue Water (BW) and Green Water (GW) resources in three typical years (wet year, dry year, and normal year) under the two LULC scenarios in 2010 and 2017 of the basin. The results showed that from 2010 to 2017, the area of cultivated land and residential construction land increased by 227.28% and 269.23%, respectively; the area of unused land, woodland, and grassland decreased by 98.84%, 35.90% and 39.52%, respectively. Compared with the results of the 2010 LULC scenario, the average BW of the three typical years under the 2017 LULC scenario decreased by 11.66%, 52.32%, and 21.95%, respectively, and the average GW flow increased by 6.72%, 2.90%, and 6.83%, respectively, and the average GW reserves decreased by 14.80%, 11.39%, and 7.67%, respectively. Therefore, this study believed that changes of LULC have led to a significant decrease in runoff and an increase in evapotranspiration in the basin.

WATER BALANCE AND ECOLOGICAL CONDITIONS OF THE RYBINSK RESERVOIR IN THE EXTREMELY HIGH-WATER YEAR OF 2017

This study analyzes the inflow, runoff and water level of the Rybinsk Reservoir during the extremely highwater year of 2017. It was the second-highest on record high-water year in the reservoir basin during the whole period of the reservoir operation. The total annual inflow to the reservoir significantly exceeded its long-term average and amounted to 52,148 km3. Such an increase in the inflow is due to rising air temperatures in winter time under the increasing influence of global warming and high rainfall. To characterize ecological conditions in the reservoir we use data on its water balance, mean ten-day period water temperature in May-October provided by Yaroslavl Center for Hydrometeorology and Environmental Monitoring and materials from six hydrological and hydrobiological expeditions conducted by researchers from the Institute for Biology of Inland Waters RAS (IBIW RAS) in May-October, 2017. During the expeditions to the reservoir, integrated hydrological, hydrochemical and hydrobiological investigations were conducted at standard stations. These studies have been carried out by IBIW researchers since 1962 to monitor the dynamics of ecological conditions of the waterbody.

ANTHROPOGENIC IMPACT ON AQUATIC ECOSYSTEMS OF REPUBLIC OF KARELIA

The article presents the results of a research carried out within the framework of state assignments, forecast topics and economic contractual topics (SevNIORKh, NFRI PetrSU, NWPI KarRC RAS, and KarelNIRO) to assess the anthropogenic impact on water bodies of the Republic of Karelia. The anthropogenic impact has been found to damage the aquatic ecosystems of Karelia: fish resources have reduced their production potential by 10.8% from the level of the 1950s, that is, in an ecologically acceptable version. Large reservoirs (Onega and Ladoga), due to the huge volumes of water masses, more actively resist technogenic transformation than small ones. Locally, there are transcendental transformations (the rivers Kovda, Kem, Nizhniy Vyg, Povenchanka, Suna and the water area of the Northern Vygozero, the Kondopoga and Petrozavodsk bays of Lake Onega, the Vodlozero Reservoir and Lake Syamozero, the Kenti-Kento system in the Yushkozersk Reservoir basin), which need some radical measures of environmental protection and restrictions of the fishing regime. After assessing the situation, it should be recognized that the level of anthropogenic pollution by waste products (industrial waste, agriculture, the consequences of timber rafting, dams of hydroelectric power plants, etc.) lead to a change in the aquatic environment for fish habitat, affect fishing productivity, lower fish catches.

Hydrodynamic behaviour of a semiarid Mediterranean watershed, under changing hydrological conditions

<p>ABSTRACT</p><p>The study analyzes the changes in the rainfall-runoff process as a result of land cover changes occurred between 1990-2018 in the Guadalest Reservoir basin with an area of 122.5 km<sup>2</sup>, using the model of the HEC-HMS model at daily scale and  to capture the complex hydrological dynamics based on GIS information . The purpose is to analyze the spatial-temporal evolution of the hydrological response in 12 sub-basins and the dynamics of land use/land cover changes for the years 1990, 2000, 2006, 2012 and 2018. </p><p>The findings reveal a change in the type of sclerophyll vegetation (forests of Quercus (calliprinos, ilex, rotundifolia, suber, etc.)from 81.56% in the 1990 initial  stage, to natural grasslands by 81.55% in the 2018 stage; a decrease in agricultural areas and their conversion into coniferous forests and natural grasslands by approximately 60% in the same period; if exists an increase of coniferous forest to the detriment of the agriculture, implies that the evapotranspiration  will increase and the run-off will decrease   with an increase in runoff in principle but as time goes by it decreases bringing as a consequence a deficit in water supply. The results of land use  change detection between the years 1990-2018 were corroborated with the values of the curve numbers obtained.</p><p>The cyclical and trend analysis of the historical series of precipitation allows evidencing a five-year cycle and a decreasing trend from 1984 to 2018.</p><p>The HEC-HMS model implementation at a daily scale and GIS-based tools have proven to be useful in achieving the study objectives. Within the HEC-HMS, the SCS Curve Number model and the Muskingum method were suitable for solving the rainfall-runoff conversion and flood propagation equations, respectively.</p><p>The researching work debeloped  is intended to identify the impact derived by the anthropic action in the change of land use and Its vegetable coverage, and how this may impact on the evotranspiration, surface run-off, and the post hydropical drainage of The Guadalest Reservoir which will use for the Integral Management of the Basin. These findings provide to the water management planners very useful information about the effects of flash floods, which have human lives cost in the ravine basin studied in recent years.</p><p> </p><h3>KEYWORDS</h3><p>Land use change, evapotranspiration, runoff, HEC-HMS hydrological model, basin, Mediterranean</p>

Evaluation and Hydrological Utility of the GPM IMERG Precipitation Products over the Xinfengjiang River Reservoir Basin, China

As a supplement to gauge observation data, many satellite observations have been used for hydrology and water resource research. This study aims to analyze the quality of the Integrated Multisatellite Retrieval for Global Precipitation Measurement (GPM IMERG) products and their hydrological utility in the Xinfengjiang River reservoir basin (XRRB), a mountainous region in southern China. The grid-based soil and water assessment tool (SWAT) model was used to construct a hydrological model of the XRRB based on two scenarios. The results showed that on a daily scale, the IMERG final run (FR) product was more accurate than the others, with Pearson’s correlation coefficients (CORR) of 0.61 and 0.71 on the grid accumulation scale and the average scale, respectively, and a relative bias (BIAS) of 0.01. In Scenario I (the SWAT model calibrated by rain gauge data), the IMERG-based simulation showed acceptable hydrologic prediction ability on the daily scale and satisfactory hydrological performance on the monthly scale. In Scenario II (the SWAT model calibrated by the FR), the hydrological performances of the FR on the daily and monthly scales were slightly better than those in Scenario I (the CORR was 0.64 and 0.85, the BIAS was 0.01 and −0.02, and the NSE was 0.43 and 0.84). These results showed the potential of the FR for hydrological modeling in tropical mountain watersheds in areas where information is scarce. This study is useful for hydrological, meteorological, and disaster studies in developing countries or remote areas with sparse or low-quality networks of ground-based observation stations.

Preferred Hierarchical Control Strategy of Non-Point Source Pollution at Regional Scale

Non-point source (NPS) pollution has wide range of sources. Under rainfall conditions, NPS pollution occurs mainly by overland flow, resulting in difficult governance. In this study, based on the cooperative analysis of critical periods (CPs) and critical source areas (CSAs), a preferred hierarchical control strategy of NPS pollution, which was connected with management units, was proposed in the Danjiangkou Reservoir Basin (DRB) to improve the pertinence of NPS pollution control. The practicality of the grid-based CSA identification results was improved by point density analysis (PDA). CPs, sub-CPs, and non-CPs were identified on the temporal scale; CSAs, sub-CSAs and non-CSAs were identified on the spatial scale. The results showed that CPs (July, April, and September), sub-CPs (May, March, and August), and non-CPs contributed 62.8%, 31.1%, and 6.1% of the annual TP loads, respectively. Furthermore, we proposed a hierarchical NPS pollution control strategy: class Ⅰ (CSAs in CPs) → class II (sub-CSAs in CPs, CSAs in sub-CPs) → class III (non-CPs, non-CSAs, sub- and non-CSAs in sub-CPs). Class Ⅰ covered the periods and areas with the highest NPS pollution loads, contributing 26.2% of the annual load within 14.5% of the area and 25.0% of the time. This study provides a reference for the targeted control of NPS pollution at regional scale, especially in environmental protection with limited funds.