Hydrological Impacts of a Changing Climate on Floods and Droughts in Philippine River Basins

Abstract

The development of new water sources to ensure more stable water supply for Metropolitan Manila is urgently needed especially with the changing climate. The objectives of this study are: 1) to develop hydrological models in 3 river basins (Angat, Kaliwa and Pampanga) surrounding Metro Manila; 2) to assess basin-scale hydrological impacts of climate change in terms of a) flooding trends and b) drought trends. Calibrations of the basins were performed in Angat dam inflows for Angat basin; and Pantabangan dam, Cabanatuan, Zaragoza, San Isidro and Arayat stream flows for Pampanga river basin. Soil moisture verification of Pampanga river basin utilized monthly surface soil moistures from both the LDAS-UT and hydrological model outputs in short vegetation areas. Incorporating bias corrected rainfall and other parameters from GCMs showed future flooding trends is virtually certain to increase while drought trends are as likely as not to increase in the uplands but very likely to increase in the flood plains.

Dynamic downscaling and bias correction of rainfall in the Pampanga River Basin, Philippines, for investigating flood risk changes due to global warming

“…This is consistent with past studies (IPCC, 2013;Jaranilla-Sanchez et al, 2013;Kitoh and Endo, 2016). The advantage of this study is the use of a downscaling model with a higher resolution.…”

“…To correct this disagreement, we employed bias correction based on popular distribution mapping (De Troch et al, 2013). As shown in Rasmy et al (2014), distribution mapping alone is appropriate for bias correction of downscaled rainfall, although a 3-step bias correction works better for GCM rainfall (Jaranilla- Sanchez et al, 2013;Nyunt et al, 2014). Because of the limited number of raingauge stations and incomplete data continuity, we mapped the downscaled basin-average rainfall onto basin average raingauge rainfall.…”

“…The advantage of this study is the use of a downscaling model with a higher resolution. Jaranilla-Sanchez et al (2013) showed that, based on bias-corrected rainfall from six GCMs, the 10th percentile peak daily discharge may increase in the Pampanga River Basin from the years of 1981-2000 to 2046-2065 in the range of zero to six times. It is not appropriate to directly compare their results with ours.…”

Design and Implementation of a Training Course on Big Data Use in Water Management

“…Koike et al (2015) described the methodology for using CMIP3 and CMIP5 data to assess the impact of climate change on hydrological regimes and water budgets in river basins; this is an important step in developing sustainable water-management solutions. Pilot studies (Koike et al, 2015) and broader national studies on planning future water resources (Jaranilla-Sanchez et al, 2013;JICA Final Report, 2013) were carried out using the proposed methodology, thus demonstrating the efficiency of the DIAS CMIP tools in exploiting large CMIP data sets.…”

Data-driven streamflow modelling in ungauged basins: regionalizing random forest (RF) models

“…Process-based methods are parametric, which make use of model and input-specific parameters to perform a water balance simulation using empirical equations (Arnold et al, 2012). Process-based models are often implemented in user interfaces, enabling input-level modifications to model not only business as usual events, but also land-use change, climate change, drought, and land management scenarios in sub-basins (herein referred as watersheds) scales (Jaranilla-Sanchez et al, 2011; Mango et al, 2011; Palao et al, 2013). For large scale-applications, e.g.…”