Suitable Land-Use and Land-Cover Allocation Scenarios to Minimize Sediment and Nutrient Loads into Kwan Phayao, Upper Ing Watershed, Thailand

Abstract

Human activity and land-use changes have affected the water quality of Kwan Phayao, Upper Ing watershed, due to the associated high sediment load and eutrophication. This study aims to identify suitable LULC allocation scenarios for minimizing sediment and nutrient export into the lake. For this purpose, the LULC status and change were first assessed, based on classified LULC data in 2009 and 2019 from Landsat images, using the SVM algorithm. Later, the land requirements of three scenarios between 2020 and 2029 were estimated, based on their characteristics, and applied to predict LULC change using the CLUE-S model. Then, actual LULC data in 2019 and predicted LULC data under three scenarios between 2020 and 2029 were used to estimate sediment and nutrient export using the SDR and NDR models. Finally, the ecosystem service change index identified a suitable LULC allocation for minimizing sediment or/and nutrient export. According to the results, LULC status and change indicated perennial trees and orchards, para rubber, and rangeland increased, while forest land and paddy fields decreased. The land requirements of the three scenarios provided reasonable results, as expected, particularly Scenario II, which adopts linear programming to calculate the land requirements for maximizing ecosystem service values. For sediment and nutrient export estimation under the predicted LULC for the three scenarios, Scenario II led to the lowest yield of sediment and nutrient exports, and provided the lowest average ESCI value among the three scenarios. Thus, the LULC allocation under Scenario II was chosen as suitable for minimizing sediment or/and nutrient export into Kwan Phayao. These results can serve as crucial information to minimize sediment and nutrient loads for land-use planners, land managers, and decision makers.

Impact of Land Use Change on the Water Environment of a Key Marsh Area in Vientiane Capital, Laos

“…This may suggest the accumulation of nitrate-nitrogen rather than the self-production of nitrate-nitrogen in waterbody and wetland due to their lower elevations in the marsh. In contrast, the built-up area discharged a large amount of nitrate-nitrogen in three different scenarios compared to other LULC classes, which is similar to the results of Kulsoontornrat and Ongsomwang [49]. Furthermore, as illustrated in Figure 8, the northern region (especially the waterbody) exhibited a high load of nitrate-nitrogen, serving as the marsh outlet.…”

“…The water quality of TLM was assessed using the nutrient delivery ratio (NDR) of the InVEST model (www.naturalcapitalproject.org (accessed on 20 October 2022)), taking nitrate-nitrogen (NO 3 − -N) as a representative pollutant. This model maps nutrient sources from watersheds, calculates their transport to streams, and evaluates nutrient retention based on environmental conditions on the land surface [49]. The nutrient loads represent the amount of nutrients contributed by each pixel of the land use image.…”

Evaluation and Validation of Estimated Sediment Yield and Transport Model Developed with Model Tree Technique

“…Therefore, for the design, operation, and management of ecofriendly and sustainable rivers, it is instrumental to have a sufficient understanding of the discharge of inflow and sediment transport and quantitatively identify and predict the sediment yield [6,7]. To solve erosion and sediment related problems, various models have been proposed for the estimation of the sediment yield or sediment transport rate [8][9][10]. Especially, numerous mathematical formulas based on statistical methods have focused on sediment yield quantification [11][12][13][14].…”