IndexLand Use and Land CoverWater QualityEcological Assessment: Macroinvertebrate AssemblagesMactoinvertebrate MetricsLand Use and Land CoverStatistical analysis of Mai Pokhari land cover change identifies three major land cover types i.e. Forest, Agricultural land and Grassland and observed significant changes over 10 years from 2000 AD to 2010 AD. A significant increase in agricultural land was observed while forest decreased significantly. The forest around Mai Pokhari was observed to be dense and increased over the 10-year interval, but decreased during movement outward. It may be because of the conservation practices administered by the wetland management committee around the wetlands. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay There is no harvesting of raw materials, including woods and fodder, from the surrounding wetland areas that contributed to the growth of the dense forest. As it moved away from the wetlands, most of the forest was observed turning into agricultural land. Dense community forests were also observed to the north and west of the wetlands and scattered forests to the east and south, which are mostly residential areas. It was found that the population of the study area is increasing (CBS 2014) and most women have been involved in agricultural practices. In place of traditional practices, large commercial farms have been established. This could be the cause of the decrease in forest area coverage. Most people near the wetlands have established hotels and lodges as their main source of income. In these cases, people plant timber trees on their private lands for the purpose of sale, turning sparse forest areas into residential ones. Depletion of forests along with massive constructions have a direct impact on aquifers causing lowering of water levels (Alam¹, Rashid, Bhat¹, & Sheikh, 2011). Roads close to wetlands, house construction and heavy vehicle traffic could also further impact wetland conditions. . Most of the males from this area move to India for seasonal reasons. This current trend is replacing traditional occupation, especially animal husbandry and trading. Most of the grasslands are becoming denuded and overgrown. With less use of pastures, they are slowly turning into forests. Conversion of land from one form to another produces a huge negative impact on wetland resources (Alam, 2011) and local ecosystem services (Zhang, Zhao, Liu, Liu, & Li, 2015). Water quality Changes in physico-chemical parameters due to natural and human activities. Dissolution of bed materials, weather events are some of the natural causes and also climate change although they are naturally influenced by human activities. The pH measured in both sampling seasons was acidic. The measured pH is below the water quality guidelines for the protection of aquatic life (6.5-9.0), which may be due to the acidic nature of the lake water due to the enormous deposition of parts Pinus roxburghii falls into the soil. There has been a large deposition of organic matter in the lake, and the decomposition of that organic matter has released carbon dioxide (CO2). The carbon dioxide thus produced combines with water and forms carbonic acid (H2CO3). Carbonic acid is also responsible for low pH. The pH ispositively correlated with ammonia and nitrates. The decomposition of organic sediments also releases nitrates and ammonium ions which enhance hydrogen ions (H+) making the water acidic (Adeogun & Fafione, 2011). The decomposition of organic matter forms acid-containing compounds and increases hydrogen ions in water (Yimer & Mengistou, 2009). There may be flux of NO3- and PO¬4- into wetlands from agriculture and pastures. The optimal pH level for the survival of the organism varies from 5 to 9 and beyond this limit the species suffers (Mesner & Geiger, 2010). The conductivity of water is always strongly influenced by the surrounding geology (Light, Licht, Bevilacqua, &Morash, 2005). The conductivity of the water was measured very low in both sampling periods, this is due to the presence of graphite rocks as bed and bank material. Graphite is mainly composed of inert materials (Light et al., 2005). Dissolved oxygen is highly reactive and changes rapidly over a very short period of time (Legesse, Giller, & O'halloran, 2000). Dissolved oxygen is one of the main factors influencing the existence of aquatic species (Giller & Malmqvist, 1998). Community aggregation and distribution of aquatic organisms are directly related to dissolved oxygen (Jackson & Myers, 2002). According to USEPA guidelines (2000), DO more than 5 mg/L is appropriate for the growth of most aquatic organisms and less than 3 mg/LL is stressful to aquatic organisms. The measured DO is less than 3 mg/l, indicating a stressful environment. A similar result was shown by Rai (2013) in his research. 5-8 mg/l DO for aquaculture and 80-100% DO saturation for a balanced aquatic ecosystem are guidelines established by the Nepal Water Quality Guidelines. The measured DO is lower than Nepal's water quality guidelines which indicate unfavorable living conditions for aquatic organisms. The result showed a slight increase in DO concentration in the pre-monsoon period, but the overall concentration was also low. The major nutrients i.e. total phosphate and nitrate were found to be higher in post-monsoon and pre-monsoon season respectively. These nutrients most influence the growth of algae and aquatic weeds (Wetzel 2001). The growth and decomposition of algae and macrophytes consumes more dissolved oxygen and therefore lowers the concentration of dissolved oxygen. Similarly, microbial organisms consume more dissolved oxygen for the decomposition of large deposits of organic matter. These could be the main factors in reducing the concentration of dissolved oxygen in the lake. A low amount of DO is a good indicator of poor lake water quality. Simply put, alkalinity is the ability to resist changing pH. Generally, most lakes and reservoirs maintain a similar pH due to the presence of carbonates which are one of the main components of alkalinity. Carbonate is formed in water after the reaction of carbon dioxide with water. The addition and reduction of carbon dioxide are simultaneous processes in wetlands where the addition of carbon dioxide reduces the pH, where the pH increases with the reduction of carbon dioxide. The alkalinity of water is also associated with hardness. The higher the total alkalinity of the water, the harder the water will be. Total hardness is the sum of calcium hardness and magnesium hardness. The main cause of hardness is the presence of calcium and magnesium which are often produced by the dissolution of limestone. In most of the sampling the presence of bed rocks that could release calcium and was detectedmagnesium in water. Water bodies contain nutrients, but an excess of nutrients is harmful. Nitrogen, phosphorus and ammonia are the main nutrients found in fresh water. These nutrients enter freshwater through various sources, including bed rocks, atmospheric deposition, surrounding vegetation, land use practices, and human activities. The overabundance of these nutrients makes the lake polluted as it encourages the excessive growth of algae. The growth and decomposition of algae reduces dissolved oxygen, making it difficult for aquatic organisms to survive. Some algae also produce toxins, which could be harmful to aquatic organisms and even humans if ingested. Nitrogen and its various forms are a major concern in the study of water analysis as they are the main causes of environmental pollution. Various amounts of nitrogen enter water through natural and anthropogenic processes. Being highly soluble in nature, nitrate reaches water from terrestrial materials, organics, and fertilizers (Schmitt, Randall, & Malzer, 2001). Excess nitrate has a long-term, long-chain impact on the aquatic ecosystem. Promotes the growth of macrophytes and wild plants. The death of these plants adds organic matter and microorganisms for decomposition. The decomposition of organic matter by microorganisms consumes more oxygen and oxygen deficiency causes the death of aquatic organisms. Mai Pokhari is a rainfall-feeding lake with high organic matter content. Organic matter could be the main source of nitrates in the lake. Due to the gradual lowering of the water level, the lake water is replenished by river water. River water moving into the lake carries nutrients from external sources. Agricultural runoff, plant debris, and animal feces were sources of nitrate releases into the river that were observed. The oxidation of ammonia also naturally forms nitrates. Nitrates were measured in the range of 0.07 mg/l to 3.2 mg/l and were found to be increased in the pre-monsoon season. Water quality guidelines and FAO have set a tolerable quality range for aquaculture below 300 mg/l. Concentration variation less than 15% from unaffected local conditions is tolerable for aquatic ecosystem according to Nepal Water Quality Guidelines. Ayers (1985) declared no impact on plants and aquatic organisms below the concentration of 5 mg/l. The measured nitrate was within the range of guidelines established by the Water Quality Guidelines. Measured ammonia was between 0.18 mg/l and 2 mg/l, above the water quality guideline range for aquatic ecosystem protection (<0.007 mg/l) and for aquaculture (<0.03 mg/l). Unlike excessive nutrient enrichment, excessive ammonia in water bodies adds toxic substances or accumulates toxins in the body of aquatic organisms and ultimately leads to death. Ammonia could be introduced into the Mai Pokhari through the decomposition of organic matter, nitrogen-containing animal feces and the process of nitrogen fixation. Various forms of phosphorus are derived from various sources. Some of the main sources of phosphorus in Mai Pokhari could be the decomposition of organic matter and release from phosphorus-containing minerals. Furthermore, soil erosion from banks could lead to phosphorus entering the water. The water from the Paha Khola also adds phosphorus to the lake water. The need for phosphorus is to promote the growth of aquatic organisms. An excess of phosphorus favorseutrophication. Eutrophication reduces the concentration of dissolved oxygen making it difficult for aquatic organisms to survive. Total phosphate concentration was measured in the range of 0.25 mg/l to 4.1 mg/l. This measured value is above water quality guidelines for aquaculture (<0.6 mg/L). For the protection of the aquatic ecosystem, a change in phosphorus concentration of less than 15% is permitted according to water quality guidelines. Ammonia, nitrate and total phosphate were positively correlated with each other (Table 7). Ammonia and nitrate are the two forms of nitrogen and both formed by the process of nitrogen fixation. At Mai Pokhari, organic matter was found to be the main stressor and releases nitrate, ammonium and total phosphate ions after decomposition. Furthermore, animal feces, release of nutrient ions from minerals and rocks, and microbial releases also created a positive correlation between nutrients. Due to the higher nutrient concentration, the DO is measured low. The measured pH was positively correlated with nitrate and ammonia while it was negatively correlated with total phosphate. It reveals that the acidic pH is the result of nitrogen ions in the water (Yimer & Mengistou, 2009). As water is measured, the acidity may be due to the fact that it contains fewer carbonate and magnesium ions, resulting in lower total water hardness. There is a measured negative correlation between pH and total hardness/total alkalinity. Total hardness and total alkalinity are positively correlated. The addition of calcium carbonate and magnesium carbonate from limestone and dolomite increases total hardness and total alkalinity. Ecological assessment: macroinvertebrate assemblages Biological indicators are essential elements for the assessment, management and conservation of water quality (Lewis, Jüttner, Reynolds, & Ormerod, 2007). Fish, macroinvertebrates and diatoms are the main faunal bioindicators. The distribution of these species is determined by the water stress factor, but most studies reveal that poor habitat quality is also responsible for the low species richness, composition and diversity (Griffith et al., 2005). Similar types of taxa were recorded in post- and pre-monsoon seasons. This could be due to similar climatic conditions, substrate type and almost similar concentration of nutrients in a lake. The greatest number of taxa and ETO taxa were measured in L1. This was due to the type of mixed substrate containing clay, silt, pebbles and freshly fallen plant parts. Site L1 was also observed to be more disturbed by human activities. Taxa richness was low at sites L4, L5, and L6 due to the clay substrate type. Diptera and Oligochaetes were recorded as dominant taxa in both sampling periods. Three families of Diptera have been recorded, namely Chironomids, Tabanidae and Simuliidae, and two families of Oligochaetes, namely Tubificidae and Naididae. A high abundance of Chironomids and Tubificids was found in the coastal area. The wide distribution of Chironomidae and Tubificidae may be their strength to survive in unstable substrates (Weatherhead & James, 2001). Generally unstable substrates have been found on disturbed and polluted sites. Mactoinvertebrate metric richness was found to increase with increasing macrophyte cover and lowering water levels in the pre-monsoon season. Macrophytes provide a safe haven for macroinvertebrates from predators and may be the reason for the greater taxa richness. This statement is also supported by previous studies (Merritt & Cummins, 1996). The distribution of the variety of macrophytes also improves the different.